Systems, devices, and methods for eyebox expansion in wearable heads-up displays

ABSTRACT

Systems, devices, and methods for eyebox expansion by exit pupil replication in wearable heads-up displays (“WHUDs”) are described. A WHUD includes a scanning laser projector (“SLP”), a holographic combiner, and an optical splitter positioned in the optical path therebetween. The optical splitter receives light signals generated by the SLP and separates the light signals into N sub-ranges based on the point of incidence of each light signal at the optical splitter. The optical splitter redirects the light signals corresponding to respective ones of the N sub-ranges towards the holographic combiner effectively from respective ones of N spatially-separated virtual positions for the SLP. The holographic combiner converges the light signals to respective ones of N spatially-separated exit pupils at the eye of the user. In this way, multiple instances of the exit pupil are distributed over the area of the eye and the eyebox of the WHUD is expanded.

BACKGROUND

Technical Field

The present systems, devices, and methods generally relate to scanninglaser-based display technologies and particularly relate to expandingthe eyebox of a scanning laser-based wearable heads-up display.

Description of the Related Art

Wearable Heads-UP Displays

A head-mounted display is an electronic device that is worn on a user'shead and, when so worn, secures at least one electronic display within aviewable field of at least one of the user's eyes, regardless of theposition or orientation of the user's head. A wearable heads-up displayis a head-mounted display that enables the user to see displayed contentbut also does not prevent the user from being able to see their externalenvironment. The “display” component of a wearable heads-up display iseither transparent or at a periphery of the user's field of view so thatit does not completely block the user from being able to see theirexternal environment. Examples of wearable heads-up displays include:the Google Glass®, the Optinvent Ora®, the Epson Moverio®, and the SonyGlasstron®, just to name a few.

The optical performance of a wearable heads-up display is an importantfactor in its design. When it comes to face-worn devices, however, usersalso care a lot about aesthetics. This is clearly highlighted by theimmensity of the eyeglass (including sunglass) frame industry.Independent of their performance limitations, many of the aforementionedexamples of wearable heads-up displays have struggled to find tractionin consumer markets because, at least in part, they lack fashion appeal.Most wearable heads-up displays presented to date employ large displaycomponents and, as a result, most wearable heads-up displays presentedto date are considerably bulkier and less stylish than conventionaleyeglass frames.

A challenge in the design of wearable heads-up displays is to minimizethe bulk of the face-worn apparatus while still providing displayedcontent with sufficient visual quality. There is a need in the art forwearable heads-up displays of more aesthetically-appealing design thatare capable of providing high-quality images to the user withoutlimiting the user's ability to see their external environment.

Eyebox

In near-eye optical devices such as rifle scopes and wearable heads-updisplays, the range of eye positions (relative to the device itself)over which specific content/imagery provided by the device is visible tothe user is generally referred to as the “eyebox.” An application inwhich content/imagery is only visible from a single or small range ofeye positions has a “small eyebox” and an application in whichcontent/imagery is visible from a wider range of eye positions has a“large eyebox.” The eyebox may be thought of as a volume in spacepositioned near the optical device. When the eye of the user (and moreparticularly, the pupil of the eye of the user) is positioned insidethis volume and facing the device, the user is able to see all of thecontent/imagery provided by the device. When the eye of the user ispositioned outside of this volume, the user is not able to see at leastsome of the content/imagery provided by the device.

The geometry (i.e., size and shape) of the eyebox is an importantproperty that can greatly affect the user experience for a wearableheads-up display. For example, if the wearable heads-up display has asmall eyebox that centers on the user's pupil when the user is gazingdirectly ahead, some or all content displayed by the wearable heads-updisplay may disappear for the user when the user gazes even slightlyoff-center, such as slightly to the left, slightly to the right,slightly up, or slightly down. Furthermore, if a wearable heads-updisplay that has a small eyebox is designed to align that eyebox on thepupil for some users, the eyebox will inevitably be misaligned relativeto the pupil of other users because not all users have the same facialstructure. Unless a wearable heads-up display is deliberately designedto provide a glanceable display (i.e., a display that is not alwaysvisible but rather is only visible when the user gazes in a certaindirection), it is generally advantageous for a wearable heads-up displayto have a large eyebox.

Demonstrated techniques for providing a wearable heads-up display with alarge eyebox generally necessitate adding more bulky optical componentsto the display. Technologies that enable a wearable heads-up display ofminimal bulk (relative to conventional eyeglass frames) to provide alarge eyebox are generally lacking in the art.

BRIEF SUMMARY

A wearable heads-up display may be summarized as including: a supportstructure that in use is worn on a head of a user; a scanning laserprojector carried by the support structure; a holographic combinercarried by the support structure, wherein the holographic combiner ispositioned within a field of view of an eye of the user when the supportstructure is worn on the head of the user; and an optical splittercarried by the support structure and positioned in an optical pathbetween the scanning laser projector and the holographic combiner, theoptical splitter comprising at least one optical element arranged toreceive light signals generated by the scanning laser projector andredirect each light signal towards the holographic combiner effectivelyfrom one of N spatially-separated virtual positions for the scanninglaser projector, where N is an integer greater than 1, the particularvirtual position for the scanning laser projector from which a lightsignal is redirected by the optical splitter determined by a point ofincidence at which the light signal is received by the optical splitter,and wherein the holographic combiner comprises at least one hologrampositioned and oriented to redirect the light signals towards the eye ofthe user.

The scanning laser projector may have a total two-dimensional scan rangeθ and at least one optical element of the optical splitter may bearranged to separate the total two-dimensional scan range θ of thescanning laser projector into N two-dimensional sub-ranges φ_(i), where

${{\sum\limits_{i = 1}^{N}\varphi_{i}} = \theta},$wherein each one of the N sub-ranges φ_(i) corresponds to a respectiveone of the N spatially-separated virtual positions for the scanninglaser projector. At least one optical element of the optical splittermay be arranged to: receive light signals corresponding to a sweep ofthe total two-dimensional scan range θ by the scanning laser projector;separate the light signals corresponding to the sweep of the totaltwo-dimensional scan range θ into the N two-dimensional sub-ranges φ_(i)based on point of incidence at the optical splitter; and redirect thelight signals corresponding to the sweep of the total two-dimensionalscan range θ towards the holographic combiner effectively from each ofthe N spatially-separated virtual positions for the scanning laserprojector, the particular virtual position for the scanning laserprojector from which each light signal in the sweep of the totaltwo-dimensional scan range θ is redirected by the optical splitterdetermined by the particular two-dimensional sub-range φ_(i) to whichthe light signal corresponds.

The scanning laser projector may have a total scan range Ω in a firstdimension, where 0°<Ω<180°, and at least one optical element of theoptical splitter may be arranged to separate the total scan range Ω ofthe scanning laser projector in the first dimension into X sub-rangesω_(i) in the first dimension, where 1<X≤N and

${{\sum\limits_{i = 1}^{X}\omega_{i}} = \Omega},$and each one of the X sub-ranges ω_(i) may correspond to a different oneof the N spatially-separated virtual positions for the scanning laserprojector. At least one optical element of the optical splitter may bearranged to: receive light signals corresponding to a sweep of the totalscan range Ω in the first dimension by the scanning laser projector;separate the light signals corresponding to the sweep of the total scanrange Ω in the first dimension into the X sub-ranges ω_(i) in the firstdimension based on point of incidence at the optical splitter; andredirect the light signals corresponding to the sweep of the total scanrange Ω in the first dimension towards the holographic combinereffectively from at least X of the N spatially-separated virtualpositions for the scanning laser projector, the particular virtualposition for the scanning laser projector from which each light signalin the sweep of the total scan range Ω in the first dimension isredirected by the optical splitter determined by the particularsub-range ω_(i) in the first dimension to which the light signalcorresponds. The scanning laser projector may have a total scan range ψin a second dimension, where 0°<ψ<180°, and at least one optical elementof the optical splitter may be arranged to separate the total scan rangeψ of the scanning laser projector in the second dimension into Ysub-ranges β_(i) in the second dimension, where 1<Y≤N and

${{\sum\limits_{i = 1}^{Y}\beta_{i}} = \psi},$and each one of the Y sub-ranges β_(i) may correspond to a different oneof the N spatially-separated virtual positions for the scanning laserprojector. At least one optical element of the optical splitter isarranged to: receive light signals corresponding to a sweep of the totalscan range ψ in the second dimension by the scanning laser projector;separate the light signals corresponding to the sweep of the total scanrange ψ in the second dimension into the Y sub-ranges β_(i) in thesecond dimension based on point of incidence at the optical splitter;and redirect the light signals corresponding to the sweep of the totalscan range ψ in the second dimension towards the holographic combinereffectively from at least Y of the N spatially-separated virtualpositions for the scanning laser projector, the particular virtualposition for the scanning laser projector from which a light signal inthe sweep of the total scan range ψ in the second dimension isredirected by the optical splitter determined by the particularsub-range β_(i) in the second dimension to which the light signalcorresponds.

The support structure may have a general shape and appearance of aneyeglasses frame. The wearable heads-up display may further include aprescription eyeglass lens. The holographic combiner may be carried bythe prescription eyeglass lens.

The at least one hologram of the holographic combiner may converge lightsignals to respective ones of N exit pupils at or proximate the eye ofthe user, the particular exit pupil determined by the particular virtualposition for the scanning laser projector from which a light signal isredirected by the optical splitter. The holographic combiner may includeat least N multiplexed holograms, and each one of the at least Nmultiplexed holograms may converge light signals corresponding to arespective one of the N spatially-separated virtual positions for thescanning laser projector to a respective one of the N exit pupils at orproximate the eye of the user. The scanning laser projector may includea red laser diode, a green laser diode, and a blue laser diode, and theholographic combiner may include a wavelength-multiplexed holographiccombiner that includes at least one red hologram, at least one greenhologram, and at least one blue hologram. In this case, for a lightsignal redirected from a particular one of the N spatially-separatedvirtual positions for the scanning laser projector by the opticalsplitter, the at least one red hologram may converge a red component ofthe light signal to a particular one of the N exit pupils at orproximate the eye of the user, the at least one green hologram mayconverge a green component of the light signal to the particular one ofthe N exit pupils at or proximate the eye of the user, and the at leastone blue hologram may converge a blue component of the light signal tothe particular one of the N exit pupils at or proximate the eye of theuser. The holographic combiner may include a wavelength-multiplexed andangle-multiplexed holographic combiner that includes at least Nangle-multiplexed red holograms, at least N angle-multiplexed greenholograms, and at least N angle-multiplexed blue holograms. In thiscase, each one of the at least N angle-multiplexed red holograms mayconverge red components of light signals redirected from a respectiveone of the N spatially-separated virtual positions for the scanninglaser projector by the optical splitter to a respective one of the Nexit pupils at or proximate the eye of the user, each one of the atleast N angle-multiplexed green holograms may converge green componentsof light signals redirected from a respective one of the Nspatially-separated virtual positions for the scanning laser projectorby the optical splitter to a respective one of the N exit pupils at orproximate the eye of the user, and each one of the at least Nangle-multiplexed blue holograms may converge blue components of lightsignals redirected from a respective one of the N spatially-separatedvirtual positions for the scanning laser projector by the opticalsplitter to a respective one of the N exit pupils at or proximate theeye of the user.

At least one of the scanning laser projector and/or the optical splittermay be physically movable and/or rotatable on the support structure, andphysical movement and/or rotation of the scanning laser projector and/oroptical splitter may change a position of at least one of the N exitpupils relative to the eye of the user.

The light signal may include an image comprising at least two pixels.

At least one optical element of the optical splitter may be arranged toreceive N light signals generated by the scanning laser projector andredirect the N light signals towards the holographic combinereffectively from respective ones of the N spatially-separated virtualpositions for the scanning laser projector, the particular virtualposition for the scanning laser projector from which each one of the Nlight signals is redirected by the optical splitter determined by arespective point of incidence at which each light signal is received bythe optical splitter. The holographic combiner may include at least onehologram positioned and oriented to converge each one of the N lightsignals to a respective exit pupil at or proximate the eye of the user.The N light signals may include N different instances of a same image,or the N light signals may include N different instances of a same pixelof an image.

The optical splitter may include a faceted optical structure with atleast N facets. At least one respective facet may correspond to eachrespective one of the N spatially-separated virtual positions for thescanning laser projector.

A wearable heads-up display may be summarized as including: a supportstructure that in use is worn on a head of a user; a scanning laserprojector carried by the support structure and having a totaltwo-dimensional scan range θ; a holographic combiner carried by thesupport structure, wherein the holographic combiner is positioned withina field of view of an eye of the user when the support structure is wornon the head of the user; an optical splitter carried by the supportstructure and positioned in an optical path between the scanning laserprojector and the holographic combiner, wherein the optical splittercomprises at least one optical element arranged to: receive lightsignals corresponding to a sweep of the total two-dimensional scan rangeθ by the scanning laser projector; separate the light signals into Ntwo-dimensional sub-ranges φ_(i) based on point of incidence at theoptical splitter, where N is an integer greater than 1 and

${{\sum\limits_{i = 1}^{N}\varphi_{i}} = \theta};$and redirect the light signals towards the holographic combiner, andwherein the holographic combiner comprises at least one hologrampositioned and oriented to converge light signals to respective ones ofN exit pupils at or proximate the eye of the user, the particular exitpupil towards which a light signal is redirected by the holographiccombiner determined by the particular two-dimensional sub-range φ_(i)into which the light signal is separated by the optical splitter.

The total two-dimensional scan range θ of the scanning laser projectormay include a total scan range Ω in a first dimension, where 0°<Ω<180°,and at least one element of the optical splitter may be arranged to:receive light signals corresponding to at least one sweep of the totalscan range Ω in the first dimension by the scanning laser projector;separate the light signals into X sub-ranges ω_(i) in the firstdimension based on point of incidence at the optical splitter, where1<X≤N and

${{\sum\limits_{i = 1}^{X}\omega_{i}} = \Omega};$and redirect the light signals towards the holographic combiner, andwherein at least one hologram of the holographic combiner is positionedand oriented to converge the light signals to respective ones of atleast X of the N exit pupils at or proximate the eye of the user, theparticular exit pupil towards which a light signal is redirected by theholographic combiner determined by at least the particular sub-rangeω_(i) in the first dimension into which the light signal is separated bythe optical splitter.

The total two-dimensional scan range θ of the scanning laser projectormay include a total scan range ψ in a second dimension, where 0°<ψ<180°,and at least one optical element of the optical splitter may be arrangedto: receive light signals corresponding to at least one sweep of thetotal scan range ψ in the second dimension by the scanning laserprojector; separate the light signals corresponding to the at least onesweep of the total scan range ψ in the second dimension into Ysub-ranges β_(i) in the second dimension based on point of incidence atthe optical splitter, where 1<Y≤N and

${{\sum\limits_{i = 1}^{Y}\beta_{i}} = \psi};$and redirect the light signals corresponding to the at least one sweepof the total scan range ψ in the second dimension towards theholographic combiner, and wherein at least one hologram of theholographic combiner is positioned and oriented to converge the lightsignals corresponding to the at least one sweep of the total scan rangeψ in the second dimension to different ones of the N exit pupils at orproximate the eye of the user, the particular exit pupil towards which alight signal is redirected by the holographic combiner determined byboth the particular sub-range ω_(i) in the first dimension and theparticular sub-range β_(i) in the second dimension into which the lightsignal is separated by the optical splitter.

A method of operating a wearable heads-up display, the wearable heads-updisplay including a scanning laser projector, an optical splitter, and aholographic combiner positioned within a field of view of an eye of auser when the wearable heads-up display is worn on a head of the user,may be summarized as including: generating a first light signal by thescanning laser projector; receiving the first light signal at a firstpoint of incidence by the optical splitter; redirecting, by the opticalsplitter, the first light signal towards the holographic combinereffectively from a first one of N spatially-separated virtual positionsfor the scanning laser projector, where N is an integer greater than 1,the first virtual position for the scanning laser projector from whichthe first light signal is redirected by the optical splitter determinedby the first point of incidence at which the first light signal isreceived by the optical splitter; and redirecting the first light signaltowards the eye of the user by the holographic combiner.

Redirecting the first light signal towards the eye of the user by theholographic combiner may include converging the first light signal to afirst one of N exit pupils at or proximate the eye of the user by theholographic combiner, the first exit pupil to which the first lightsignal is converged by the holographic combiner determined by the firstvirtual position for the scanning laser projector from which the firstlight signal is redirected by the optical splitter. The holographiccombiner may include at least N multiplexed holograms, and convergingthe first light signal to a first one of N exit pupils at or proximatethe eye of the user by the holographic combiner may include convergingthe first light signal to the first exit pupil by a first one of the Nmultiplexed holograms of the holographic combiner, the first multiplexedhologram by which the first light signal is converged determined by thefirst virtual position for the scanning laser projector from which thefirst light signal is redirected by the optical splitter. The scanninglaser projector may include a red laser diode, a green laser diode, anda blue laser diode, the first light signal generated by the scanninglaser projector may include a red component, a green component, and ablue component, and the holographic combiner may include awavelength-multiplexed holographic combiner that includes at least onered hologram, at least one green hologram, and at least one bluehologram. In this case, converging the first light signal to a first oneof N exit pupils at or proximate the eye of the user by one of the Nmultiplexed holograms of the holographic combiner may include:converging a red component of the first light signal to the first exitpupil by the at least one red hologram; converging a green component ofthe first light signal to the first exit pupil by the at least one greenhologram; and converging a blue component of the first light signal tothe first exit pupil by the at least one blue hologram. The holographiccombiner may include a wavelength-multiplexed and angle-multiplexedholographic combiner that includes at least N angle-multiplexed redholograms, at least N angle-multiplexed green holograms, and at least Nangle-multiplexed blue holograms. In this case, converging a redcomponent of the first light signal to the first exit pupil by the atleast one red hologram may include converging the red component of thefirst light signal to the first exit pupil by a first one of the Nangle-multiplexed red holograms, the first angle-multiplexed redhologram by which the red component of the first light signal isconverged determined by the first virtual position for the scanninglaser projector from which the first light signal is redirected by theoptical splitter; converging a green component of the first light signalto the first exit pupil by the at least one green hologram may includeconverging the green component of the first light signal to the firstexit pupil by a first one of the N angle-multiplexed green holograms,the first angle-multiplexed green hologram by which the green componentof the first light signal is converged determined by the first virtualposition for the scanning laser projector from which the first lightsignal is redirected by the optical splitter; and converging a bluecomponent of the first light signal to the first exit pupil by the atleast one blue hologram may include converging the blue component of thefirst light signal to the first exit pupil by a first one of the Nangle-multiplexed blue holograms, the first angle-multiplexed bluehologram by which the blue component of the first light signal isconverged determined by the first virtual position for the scanninglaser projector from which the first light signal is redirected by theoptical splitter.

The method may further include: generating a second light signal by thescanning laser projector; receiving the second light signal at a secondpoint of incidence by the optical splitter; redirecting, by the opticalsplitter, the second light signal towards the holographic combinereffectively from a second one of the N spatially-separated virtualpositions for the scanning laser projector, the second virtual positionfor the scanning laser projector from which the second light signal isredirected by the optical splitter determined by the second point ofincidence at which the second light signal is received by the opticalsplitter; and converging the second light signal to a second one of theN exit pupils at or proximate the eye of the user by the holographiccombiner. The scanning laser projector may have a total scan range θ.Receiving the first light signal at a first point of incidence by theoptical splitter may include receiving, by the optical splitter, thefirst light signal at a first point of incidence that is included in afirst one φ₁ of N sub-ranges φ_(i) of the total scan range θ for thescanning laser projector, where

${\sum\limits_{i = 1}^{N}\varphi_{i}} = {\theta.}$Redirecting, by the optical splitter, the first light signal towards theholographic combiner effectively from a first one of Nspatially-separated virtual positions for the scanning laser projector,the first virtual position for the scanning laser projector from whichthe first light signal is redirected by the optical splitter determinedby the first point of incidence at which the first light signal isreceived by the optical splitter may include redirecting, by the opticalsplitter, the first light signal towards the holographic combinereffectively from a first one of N spatially-separated virtual positionsfor the scanning laser projector, the first virtual position for thescanning laser projector from which the first light signal is redirectedby the optical splitter determined by the first sub-range φ₁ of thetotal scan range θ for the scanning laser projector. Receiving thesecond light signal at a second point of incidence by the opticalsplitter may include receiving, by the optical splitter, the secondlight signal at a second point of incidence that is included in a secondone φ₂ of the N sub-ranges φ_(i) of the total scan range θ for thescanning laser projector. Redirecting, by the optical splitter, thesecond light signal towards the holographic combiner effectively from asecond one of the N spatially-separated virtual positions for thescanning laser projector, the second virtual position for the scanninglaser projector from which the second light signal is redirected by theoptical splitter determined by the second point of incidence at whichthe second light signal is received by the optical splitter may includeredirecting, by the optical splitter, the second light signal towardsthe holographic combiner effectively from a second one of the Nspatially-separated virtual positions for the scanning laser projector,the second virtual position for the scanning laser projector from whichthe second light signal is redirected by the optical splitter determinedby the second sub-range φ₂ of the total scan range θ for the scanninglaser projector.

Generating a first light signal by the scanning laser projector mayinclude generating a first instance of an image by the scanning laserprojector, the first instance of the image including at least twopixels.

Generating a first light signal by the scanning laser projector mayinclude generating a first instance of a first pixel of an image by thescanning laser projector.

A method of operating a wearable heads-up display, the wearable heads-updisplay including a scanning laser projector, an optical splitter, and aholographic combiner positioned within a field of view of an eye of auser when the wearable heads-up display is worn on a head of the user,may be summarized as including: generating light signals by the scanninglaser projector, the light signals corresponding to a sweep of the totaltwo-dimensional scan range θ for the scanning laser projector; receivingthe light signals corresponding to the sweep of the totaltwo-dimensional scan range θ of the scanning laser projector by theoptical splitter; separating, by the optical splitter, the light signalsinto N two-dimensional sub-ranges φ_(i) based on point of incidence atthe optical splitter, where N is an integer greater than 1 and

${{\sum\limits_{i = 1}^{N}\varphi_{i}} = \theta};$redirecting the light signals towards the holographic combiner by theoptical splitter; and converging each light signal to one of N exitpupils at or proximate the eye of the user by the holographic combiner,the particular one of the N exit pupils to which a light signal isconverged by the holographic combiner determined by the particulartwo-dimensional sub-range φ_(i) into which the light signal is separatedby the optical splitter. The holographic combiner may include at least Nmultiplexed holograms, and converging each light signal to one of N exitpupils at or proximate the eye of the user by the holographic combinermay include converging each light signal to one of the N exit pupils byone of the at least N multiplexed holograms

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not necessarily drawn to scale, and some ofthese elements are arbitrarily enlarged and positioned to improvedrawing legibility. Further, the particular shapes of the elements asdrawn are not necessarily intended to convey any information regardingthe actual shape of the particular elements, and have been solelyselected for ease of recognition in the drawings.

FIG. 1 is a partial-cutaway perspective view of a wearable heads-updisplay that provides a large eyebox made up of multipleoptically-replicated exit pupils in accordance with the present systems,devices, and methods.

FIG. 2A is an illustrative diagram of a wearable heads-up displayshowing an optical splitter in operation for the purpose of eyeboxexpansion by exit pupil replication in accordance with the presentsystems, devices, and methods.

FIG. 2B is an illustrative diagram of the wearable heads-up display fromFIG. 2A showing a sweep of a first sub-range φ₁ of the total scan rangeθ by the scanning laser projector (e.g., a partial sweep of the totalscan range θ) and the corresponding redirection of light signals fromthe first virtual position by the optical splitter in accordance withthe present systems, devices, and methods.

FIG. 2C is an illustrative diagram of the wearable heads-up display fromFIGS. 2A and 2B showing a sweep of a second sub-range φ₂ of the totalscan range θ by the scanning laser projector (e.g., a partial sweep ofthe total scan range θ) and the corresponding redirection of lightsignals from the second virtual position by the optical splitter inaccordance with the present systems, devices, and methods.

FIG. 2D is an illustrative diagram of the wearable heads-up display fromFIGS. 2A 2B, and 2C showing a sweep of a third sub-range φ₃ of the totalscan range θ by the scanning laser projector (e.g., a partial sweep ofthe total scan range θ) and the corresponding redirection of lightsignals from the third virtual position by the optical splitter inaccordance with the present systems, devices, and methods.

FIG. 2E is an illustrative diagram of the wearable heads-up display fromFIGS. 2A, 2B, 2C, and 2D showing eyebox expansion by temporallysequential exit pupil replication with respective instances of the samedisplay content projected spatially in parallel with one another towardsrespective exit pupils in accordance with the present systems, devices,and methods.

FIG. 3 is an illustrative diagram showing an exemplary holographiccombiner in two-dimensions converging four instances of replicated(e.g., repeated) light signals to form an expanded eyebox comprisingfour spatially-separated exit pupils at or proximate the eye of a userin accordance with the present systems, devices, and methods.

FIG. 4 is a schematic diagram of an example of an optical splitter forseparating the total scan range θ of a scanning laser projector intothree sub-ranges φ₁, φ₂, and φ₃ in accordance with the present systems,devices, and methods.

FIG. 5 is an illustrative diagram of an example of an optical splitterfor separating the total two-dimensional scan range θ of a scanninglaser projector into four two-dimensional sub-ranges φ₁, φ₂, φ₃, and φ₄in accordance with the present systems, devices, and methods.

FIG. 6 is a flow-diagram showing a method of operating a wearableheads-up display in accordance with the present systems, devices, andmethods.

FIG. 7 is a flow-diagram showing a method of operating a wearableheads-up display in accordance with the present systems, devices, andmethods.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures associated with portable electronicdevices and head-worn devices, have not been shown or described indetail to avoid unnecessarily obscuring descriptions of the embodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense, that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its broadest sense, that is as meaning “and/or”unless the content clearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

The various embodiments described herein provide systems, devices, andmethods for eyebox expansion in scanning laser-based wearable heads-updisplays (“WHUDs”). Generally, a scanning laser-based WHUD is a form ofvirtual retina display in which a scanning laser projector (“SLP”) drawsa raster scan onto the eye of the user. In the absence of any furthermeasure the SLP projects light over a fixed area called the exit pupilof the display. In order for the user to see displayed content the exitpupil typically needs to align with, be encompassed by, or overlap withthe entrance pupil of the user's eye. The full resolution and/or fieldof view of the display is visible to the user when the exit pupil of thedisplay is completely contained within the entrance pupil of the eye.For this reason, a scanning laser-based WHUD typically employs arelatively small exit pupil that is equal to or smaller than theexpected size of the entrance pupil of the user's eye (e.g., less thanor equal to about 4 mm in diameter).

The eyebox of a scanning laser-based WHUD is defined by the geometry ofthe exit pupil of the display at or proximate the eye of the user. Ascanning laser-based WHUD that employs a small exit pupil in order toachieve maximum display resolution and/or field of view typically hasthe drawback of having a relatively small eyebox. For example, the exitpupil may be aligned with the center of the user's eye so that the eye'spupil is located “within the eyebox” when the user is gazing directlyahead but the eye's pupil may quickly leave the eyebox if and when theuser glances anywhere off-center. A larger eyebox may be achieved byincreasing the size of the exit pupil but this typically comes at thecost of reducing the display resolution and/or field of view. Inaccordance with the present systems, devices, and methods, the eyebox ofa scanning laser-based WHUD may be expanded by optically replicating orrepeating a relatively small exit pupil and spatially distributingmultiple copies or instances of the exit pupil over a relatively largerarea of the user's eye, compared to the area of the single exit pupil onits own. In this way, at least one complete instance of the display exitpupil (either as a single instance in its entirety or as a combinationof respective portions of multiple instances) may be contained withinthe perimeter of the eye's pupil for each of a range of eye positionscorresponding to a range of gaze directions of the user. In other words,the present systems, devices, and methods describe eyebox expansion byexit pupil replication in scanning laser-based WHUDs.

Throughout this specification and the appended claims, the term“replication” is used (e.g., in the context of “exit pupil replication”)to generally refer to situations where multiple instances ofsubstantially the same thing (e.g., an exit pupil) are produced. Theterm “exit pupil replication” is intended to generally encompassapproaches that produce concurrent (e.g., temporally parallel) instancesof an exit pupil as well as approaches that produce sequential (e.g.,temporally serial or “repeated”) instances of an exit pupil. In manyexamples, the present systems, devices, and methods provide exit pupilreplication by exit pupil repetition or sequential exit pupil tiling.Unless the specific context requires otherwise, references to “exitpupil replication” herein include exit pupil replication by exit pupilrepetition.

FIG. 1 is a partial-cutaway perspective view of a WHUD 100 that providesa large eyebox made up of multiple optically-replicated exit pupils inaccordance with the present systems, devices, and methods. WHUD 100includes a support structure 110 that in use is worn on the head of auser and has a general shape and appearance of an eyeglasses (e.g.,sunglasses) frame. Support structure 110 carries multiple components,including: a SLP 120, a holographic combiner 130, and an opticalsplitter 150. Portions of SLP 120 and optical splitter 150 may becontained within an inner volume of support structure 110; however, FIG.1 provides a partial-cutaway view in which regions of support structure110 have been removed in order to render visible portions of SLP 120 andoptical splitter 150 that may otherwise be concealed.

Throughout this specification and the appended claims, the term“carries” and variants such as “carried by” are generally used to referto a physical coupling between two objects. The physical coupling may bedirect physical coupling (i.e., with direct physical contact between thetwo objects) or indirect physical coupling that may be mediated by oneor more additional objects. Thus, the term carries and variants such as“carried by” are meant to generally encompass all manner of direct andindirect physical coupling, including without limitation: carried on,carried within, physically coupled to, and/or supported by, with orwithout any number of intermediary physical objects therebetween.

SLP 120 may include multiple laser diodes (e.g., a red laser diode, agreen laser diode, and/or a blue laser diode) and at least one scanmirror (e.g., a single two-dimensional scan mirror or twoone-dimensional scan mirrors, which may be, e.g., MEMS-based orpiezo-based). SLP 120 may be communicatively coupled to (and supportstructure 110 may further carry) a processor and a non-transitoryprocessor-readable storage medium or memory storing processor-executabledata and/or instructions that, when executed by the processor, cause theprocessor to control the operation of SLP 120. For ease of illustration,FIG. 1 does not call out a processor or a memory.

Holographic combiner 130 is positioned within a field of view of atleast one eye of the user when support structure 110 is worn on the headof the user. Holographic combiner 130 is sufficiently opticallytransparent to permit light from the user's environment (i.e.,“environmental light”) to pass through to the user's eye. In theillustrated example of FIG. 1, support structure 110 further carries atransparent eyeglass lens 140 (e.g., a prescription eyeglass lens) andholographic combiner 130 comprises at least one layer of holographicmaterial that is adhered to, affixed to, laminated with, carried in orupon, or otherwise integrated with eyeglass lens 140. The at least onelayer of holographic material may include a photopolymer film such asBayfol®HX available from Bayer MaterialScience AG or a silver halidecompound and may, for example, be integrated with transparent lens 140using any of the techniques described in U.S. Provisional PatentApplication Ser. No. 62/214,600. Holographic combiner 130 includes atleast one hologram in or on the at least one layer of holographicmaterial. With holographic combiner 130 positioned in a field of view ofan eye of the user when support structure 110 is worn on the head of theuser, the at least one hologram of holographic combiner 130 ispositioned and oriented to redirect light originating from SLP 120towards the eye of the user. In particular, the at least one hologram ispositioned and oriented to receive light signals that originate from SLP120 and converge those light signals to at least one exit pupil at orproximate the eye of the user.

Optical splitter 150 is positioned in an optical path between SLP 120and holographic combiner 130. Optical splitter 150 comprises at leastone optical element (e.g., at least one lens, reflector, partialreflector, prism, diffractor, diffraction grating, mirror, or otheroptical element, or at least one configuration, combination, and/orarrangement of such) that is arranged to receive light signals generatedand output by SLP 120 and redirect each such light signal towardsholographic combiner 130 effectively from one of multiple (e.g., N,where N is an integer greater than 1) spatially-separated “virtualpositions” for SLP 120. Advantageously, optical splitter 150 may be astatic and passive component that, without power consumption or anymoving parts, receives (at a first point of incidence therein orthereon) a first light signal generated by SLP 120 and routes/redirectsthe first light signal along an optical path towards holographiccombiner 130 that traces back to (if optical splitter 150 is ignoredduring trace back) one of N spatially-separated virtual positions forSLP 120. The particular one of the N spatially-separated virtualpositions for SLP 120 from which the first light signal is redirected byoptical splitter 150 is determined by the first point of incidence atwhich the first light signal is received by optical splitter 150. Inother words, from the point of view of holographic combiner 130, opticalsplitter 150 causes at least some light signals generated by SLP 120 toappear to originate (i.e., “effectively” originate) from Nspatially-separated “virtual positions” for SLP 120 as opposed to fromthe real position for SLP 120.

Throughout this specification and the appended claims, reference isoften made to one or more “virtual position(s)” such as “Nspatially-separated virtual positions for a SLP.” The “real position” ofan object is its actual position in real, three dimensional space. A“virtual position” of an object is a position in real space at which theoptics of a system cause light from the object to effectively originateeven though the real position of the object may be elsewhere. In otherwords, the optics of the system cause light from the object to followoptical paths that would trace back, if the optics of the system wereignored during the trace back, to a “virtual position” in space that isspatially-separated from the object's “real position” in space. As asimple example, an object in front of a planar mirror has a “virtualposition” on the other side of the planar mirror. A “virtual position”may be a result of one or more intervening optical element(s) in anoptical path. When one or more optical element(s) redirects lightsignals from a SLP, a virtual position for the SLP refers to theposition in real space at which the SLP would need to be located inorder to provide light signals having that same trajectory without anyintervening optics. The optics of the system cause the light signals tofollow a trajectory that would correspond to a different point of originif there were no such optics in the system. The light signals appear tohave “effectively” originated from a different, or “virtual,” positionfor the SLP.

FIG. 2A is an illustrative diagram of a WHUD 200 showing an opticalsplitter 250 in operation for the purpose of eyebox expansion by exitpupil replication in accordance with the present systems, devices, andmethods. WHUD 200 may be substantially similar to WHUD 100 from FIG. 1,although in FIG. 2A no support structure (e.g., support structure 110)is illustrated in order to reduce clutter. As with WHUD 100, WHUD 200comprises a SLP 220 (which includes a RGB laser module 221 and at leastone MEMS-based scan mirror 222), a holographic combiner 230 carried byan eyeglass lens 240, and the optical splitter 250. As previouslydescribed, the combination of holographic combiner 230 and eyeglass lens240 is sufficiently transparent to allow environmental light 295 to passthrough to the eye 290 of the user.

SLP 220 is located at a position 260 (i.e., a “real” position) relativeto holographic combiner 230 and is shown generating (e.g., projecting) aset of light signals 270. Light signals 270 correspond to a first sweepof a total scan range (e.g., a total two-dimensional scan range, withonly one dimension visible in the view of FIG. 2A) θ by SLP 220 and maycollectively represent, for example, a projection by SLP 220 of a firstimage, or a first frame of a video, or generally a first frame ofdisplay content for WHUD 200.

Optical splitter 250 is positioned in an optical path between SLP 220and holographic combiner 230 such that optical splitter 250 interrupts(e.g., receives) light signals 270 en route from SLP 220 to holographiccombiner 230. As previously described, optical splitter 250 includes atleast one optical element (e.g., at least one lens, reflector, partialreflector, prism, diffractor, diffraction grating, mirror, or otheroptical element, or at least one configuration, combination, and/orarrangement of such) that is arranged to redirect light signals 270towards holographic combiner 230 effectively from N spatially-separatedvirtual positions 261, 262, and 263 for SLP 220. Particularly, opticalsplitter 250 separates, divides, branches, furcates, or generally“splits” light signals 270 into N groups, sets, ranges, or “sub-ranges”and redirects each sub-range of light signals 270 along a respectiverange (or sub-range) of optical paths that effectively originates from arespective one of the N spatially-separated virtual positions 261, 262,and 263 for SLP 220.

In operation, scan mirror 222 of SLP 220 projects, guides, directs, orgenerally “sweeps” modulated light signals 270 over a range (orcombination of ranges) of directions and/or angles in order to define adisplay image. A single scan mirror 222 is shown in FIG. 2A forsimplicity though in alternative implementations an arrangement of twoor more scan mirrors may be employed. The total range of availabledirections and/or angles over which SLP 220 (e.g., at least one scanmirror 222 of SLP 220) is operative to project light signals 270 isgenerally referred to herein as the total “scan range” and is denoted inFIG. 2A by the symbol θ. Throughout this specification and the appendedclaims, the symbol θ is used to represent the total scan range (e.g.,the total two-dimensional scan range) of a SLP (e.g., SLP 220) andincludes all available directions and/or angles at which the SLP isoperative to output light signals during normal use. Depending on thespecific display content being projected by the SLP (e.g., depending onthe specific modulation pattern of laser module 221), any particulardirection and/or angle in the total scan range θ may correspond to anyparticular light signal (e.g., a red light signal, a green light signal,a blue light signal, any combination thereof, or no light signal at all)at any particular time. One “sweep” of the total scan range θ of a SLP220 may produce one projected image, or one frame of a projected videoor animation, or generally one frame of display content, where thecomposition of the display content depends on the modulation pattern oflaser module 221 during the sweep. The SLPs described herein aregenerally operative to draw a raster scan and the “total scan range”generally encompasses the outer perimeter of the full raster scan thatthe SLP is operative to draw. This may be accomplished by, for example,a SLP that employs a single scan mirror operative to scan in twoorthogonal dimensions or two separate scan mirrors that are eachoperative to scan in a respective one of two orthogonal dimensions.

The total two-dimensional scan range θ of a SLP may be broken down intoa total scan range Ω in a first dimension corresponding to all availabledirections and/or angles of light signals in a first dimension (e.g.,the horizontal dimension) that the SLP is operative to output duringnormal use, and a total scan range ψ in a second dimension correspondingto all available directions and/or angles of light signals in a seconddimension (e.g., the vertical dimension) that the SLP is operative tooutput during normal use. Generally, 0°<Ω<180° and 0°<ψ<180°, althoughin practice Ω and ψ may each be within a narrower range, such as10°<Ω<60°, and 10°<ψ<60°. The relative values of Ω and ψ influence theaspect ratio of the WHUD. In other words, the total two-dimensional scanrange θ may be made up of a first one-dimensional component Ω and asecond (e.g., orthogonal) one-dimensional component ψ, as θ=Ω×ψ.Generally, one “sweep” of a total scan range in a single dimension by aSLP refers to one instance of the scan mirror(s) of the SLP movingthrough all orientations or configurations that correspond to allavailable directions/angles for light signals in the dimensionassociated with that scan range. A sweep of the total scan range Ω inthe first dimension by the SLP therefore corresponds to a sweep (e.g.,by at least one scan mirror of the SLP) over or across all orientationsor configurations that correspond to all available directions/angles forlight signals in that first dimension and a sweep of the total scanrange ψ in the second dimension by the SLP therefore corresponds to asweep (e.g., by at least one scan mirror of the SLP) over or across allorientations or configurations that correspond to all availabledirections/angles for light signals in that second dimension. A sweep ofa total two-dimensional scan range θ, however, may involve multiplesweeps of the total scan ranges Ω and ψ in each of the first and thesecond dimensions, respectively. A common mode of operation for a SLP isto perform a respective sweep of the total scan range Ω in a firstdimension (e.g., the horizontal dimension) at each discrete step orposition along a sweep of the total scan range ψ in a second dimension(e.g., the vertical dimension). Whether or not a light signal isactually projected at any given direction/angle depends on themodulation pattern for the particular display content being projected atthat time.

Returning to FIG. 2A, optical splitter 250 includes at least one opticalelement that is arranged to receive light signals 270 corresponding to asweep of the total scan range θ by SLP 220, separate the light signalsinto N sub-ranges φ_(i) based on the point of incidence of each lightsignal 270 at optical splitter 250, where

${{\sum\limits_{i = 1}^{N}\varphi_{i}} = \theta},$and redirect the light signals towards holographic combiner 230effectively from each of the N spatially-separated virtual positions261, 262, and 263 for SLP 220. Each one of the N sub-ranges φ_(i) maycorrespond to a respective one of the N spatially-separated virtualpositions 261, 262, and 263 for SLP 220. The particular one of the Nvirtual positions 261, 262, and 263 for SLP 220 from which each lightsignal 270 in the sweep of the total scan range θ is redirected byoptical splitter 250 is determined by the particular one of the Nsub-ranges φ_(i) to which the light signal 270 corresponds. In the viewof the illustrated example, N=3 sub-ranges (e.g., φ₁, φ₂, and φ₃respectively, but not individually called out to reduce clutter) andeach sub-range includes a respective set of light signals 271, 272, and273 that together make up light signals 270. That is, optical splitter250 splits or separates light signals 270 into a first sub-range φ₁comprising light signals 271 (represented by lines with large dashes), asecond sub-range φ₂ comprising light signals 272 (represented by solidlines), and a third sub-range φ₃ comprising light signals 273(represented by dotted lines). Optical splitter 250 redirects the lightsignals so that first light signals 271 effectively originate from firstvirtual position 261, second light signals 272 effectively originatefrom second virtual position 262, and third light signals 273effectively originate from third virtual position 263. Successiveindividual ones of the N=3 sub-ranges φ₁, φ₂, and φ₃ corresponding torespective ones of first light signals 271, second light signals 272,and third light signals 273 are depicted in FIGS. 2B, 2C, and 2Drespectively.

Each of the N=3 virtual positions 261, 262, and 263 for SLP 220 isspatially-separated from real position 260 for SLP 220, so the opticalpaths between each of virtual positions 261, 262, and 263 for SLP 220(corresponding to first light signal 271, second light signals 272, andthird light signals 273, respectively) and holographic combiner 230 aredifferent from the optical paths between real position 260 for SLP 220and holographic combiner 230. For example, the optical paths of lightsignals 271 are different from the optical paths of light signals 272and the optical paths of light signals 273 are different from theoptical paths of both light signals 271 and light signals 272.Advantageously, each of the N=3 virtual positions 261, 262, and 263, forSLP 220 may correspond to a respective position and orientation of SLP220. In other words, relative to the other ones of the N=3 virtualpositions 261, 262, and 263 for SLP 220, each one of the virtualpositions 261, 262, and 263 may correspond to a respective displacementand rotation of SLP 220. Such is the case in WHUD 200 for which, aswould be apparent to one of ordinary skill in the art, a line connectingeach of the N=3 virtual positions 261, 262, and 263 for SLP 220 in FIG.2A would be a curved line.

As previously described, holographic combiner 230 includes at least onehologram that is operative (e.g., designed, crafted, encoded, recorded,and/or generally positioned and oriented) to redirect light signals 270received from optical splitter 250 towards the eye 290 of the user. Inthe illustrated implementation, the at least one hologram of holographiccombiner 230 converges respective ones of light signals 271, 272, and273 to respective ones of N=3 exit pupils 281, 282, and 283 at orproximate eye 290. The particular exit pupil 281, 282, and 283 to whicha light signal is converged by holographic combiner 230 depends on(e.g., is determined by) the particular virtual position 261, 262, and263 for SLP 220 from which the light signal is redirected by opticalsplitter 250. Thus, optical splitter 250 splits light signals 270 intoN=3 groups (light signals 271, 272, and 273) or sub-ranges (φ₁, φ₂, andφ₃) and redirects each group or sub-range to holographic combiner 230 insuch a way (e.g., effectively from such a virtual position) that eachgroup or sub-range is converged by holographic combiner 230 to arespective one of N=3 spatially-separated exit pupils 281, 282, and 283at eye 290. The total eyebox 280 of WHUD 200 encompasses all threespatially-separated exit pupils 281, 282, and 283. If optical splitter250 was not present then the total eyebox 280 of WHUD 200 would becomposed of a single exit pupil (e.g., 282). Optical splitter 250expands the eyebox 280 of WHUD 200 by breaking up (or “splitting”) thetotal scan range θ of SLP 220 into N=3 sub-ranges φ_(i) and,correspondingly, replicating or repeating a single exit pupil (e.g.,282) as N=3 exit pupils 281, 282, and 283 over a larger spatial area ateye 290. As will be discussed in more detail later on, in order toreplicate the same display content at each exit pupil 281, 282, and 283,SLP 220 may re-modulate nominally the same display content N times(e.g., repeated as N instances of nominally the same modulation pattern)in a sweep of the total scan range θ with each respective modulation(e.g., each one of the N instances) corresponding to a respective one ofthe N sub-ranges φ_(i) of the total scan range θ. N=3 sub-ranges φ₁, φ₂,and φ₃ and N=3 exit pupils 281, 282, and 283 are used as illustrativeexamples only in FIG. 2A. A person of skill in the art will appreciatethat in alternative implementations N may be any other integer greaterthan 1, such as N=2, 4, 5, 6, and so on.

Generally, a sweep of the total scan range θ by SLP 220 may include more(e.g., significantly more, such as on the order of tens more, hundredsmore, thousands more, or even greater) than N light signals. Within sucha sweep, at least one optical element of optical splitter 250 may bearranged to receive at least N light signals generated by SLP 220 andredirect at least N light signals towards holographic combiner 230effectively from respective ones of the N spatially-separated virtualpositions for SLP 220. In this case, each one of the N light signals isin a respective one of the N sub-ranges φ_(i) of the total scan range θ.That is, a first one of the N light signals is in a first one of the Nsub-ranges φ₁ (e.g., one of light signals 271) and is redirected byoptical splitter 250 to effectively originate from first virtualposition 261 for SLP 220, a second one of the N light signals is in asecond one of the N sub-ranges φ₂ (e.g., one of light signals 272) andis redirected by optical splitter 250 to effectively originate fromsecond virtual position 262 for SLP 220, and a third one of the N lightsignals is in a third one of the N sub-ranges φ₃ (e.g., one of lightsignals 273) and is redirected by optical splitter 250 to effectivelyoriginate from third virtual position 263 for SLP 220, and so on asappropriate to the specific implementation (e.g., for all N). Theparticular virtual position 261, 262, and 263 for SLP 220 from whicheach one of the N light signals is redirected by optical splitter 250depends on (e.g., is determined by) the particular point of incidence atwhich each light signal is received by optical splitter 250. Holographiccombiner 230 receives the N light signals from optical splitter 250 andconverges each one of the N light signals to a respectivespatially-separated exit pupil 281, 282, and 283 at or proximate eye290. In this example, the N light signals may include, for example, Ndifferent instances of a same image (i.e., N repeated or replicatedinstances of the same image comprising at least two pixels) or the Nlight signals may include, for example, N different instances of a samepixel of an image (e.g., N repeated or replicated instances of the samepixel in the same image).

FIG. 2A depicts an illustrative example of a sweep of the total scanrange (e.g., the total two-dimensional scan range, with only onedimension visible in the view of FIG. 2A) θ by SLP 220. As describedpreviously, FIGS. 2B, 2C, and 2D respectively depict successive ones ofthe N=3 sub-ranges φ₁, φ₂, and φ₃ that make up the sweep of the totalscan range θ of SLP 220 from FIG. 2A.

FIG. 2B is an illustrative diagram of WHUD 200 from FIG. 2A showing asweep of a first sub-range φ₁ of the total scan range θ by SLP 220(e.g., a partial sweep of the total scan range θ) and the correspondingredirection of light signals 271 from first virtual position 261 byoptical splitter 250 in accordance with the present systems, devices,and methods. In the illustrated example, first sub-range φ₁ correspondsto the light signals 271 (represented by lines with large dashes in bothFIG. 2B and FIG. 2A) generated by SLP 220 over the first third of thetotal scan range θ, therefore φ₁=θ/3. For the range of directions and/orangles of light signals 271 in first sub-range φ₁, optical splitter 250receives light signals 271 at various points of incidence over a firstrange of points of incidence. Based at least in part on thepositions/locations of the points of incidence in the first range ofpoints of incidence, optical splitter 250 redirects light signals 271towards holographic combiner 230 effectively from first virtual position261 for SLP 220. Holographic combiner 230 receives light signals 271 infirst sub-range φ₁ from optical splitter 250 and converges light signals271 to first exit pupil 281 at or proximate eye 290.

FIG. 2C is an illustrative diagram of WHUD 200 from FIGS. 2A and 2Bshowing a sweep of a second sub-range φ₂ of the total scan range θ bySLP 220 (e.g., a partial sweep of the total scan range θ) and thecorresponding redirection of light signals 272 from second virtualposition 262 by optical splitter 250 in accordance with the presentsystems, devices, and methods. In the illustrated example, secondsub-range φ₂ corresponds to the light signals 272 (represented by solidlines in both FIG. 2C and FIG. 2A) generated by SLP 220 over the secondthird of the total scan range θ, therefore φ₂=θ/3. For the range ofdirections and/or angles of light signals 272 in second sub-range φ₂,optical splitter 250 receives light signals 272 at various points ofincidence over a second range of points of incidence. Based at least inpart on the positions/locations of the points of incidence in the secondrange of points of incidence, optical splitter 250 redirects lightsignals 272 towards holographic combiner 230 effectively from secondvirtual position 262 for SLP 220. Holographic combiner 230 receiveslight signals 272 in second sub-range φ₂ from optical splitter 250 andconverges light signals 272 to second exit pupil 282 at or proximate eye290. Because second virtual position 262 is spatially-separated fromfirst virtual position 261, second exit pupil 282 is spatially-separatedfrom first exit pupil 281 at or proximate eye 290.

FIG. 2D is an illustrative diagram of WHUD 200 from FIGS. 2A 2B, and 2Cshowing a sweep of a third sub-range φ₃ of the total scan range θ by SLP220 (e.g., a partial sweep of the total scan range θ) and thecorresponding redirection of light signals 273 from third virtualposition 263 by optical splitter 250 in accordance with the presentsystems, devices, and methods. In the illustrated example, thirdsub-range φ₃ corresponds to the light signals 273 (represented by dottedlines in both FIG. 2D and FIG. 2A) generated by SLP 220 over the lastthird of the total scan range θ, therefore φ₃=θ/3. For the range ofdirections and/or angles of light signals 273 in third sub-range φ₃,optical splitter 250 receives light signals 273 at various points ofincidence over a third range of points of incidence. Based at least inpart on the positions/locations of the points of incidence in the thirdrange of points of incidence, optical splitter 250 redirects lightsignals 273 towards holographic combiner 230 effectively from thirdvirtual position 263 for SLP 220. Holographic combiner 230 receiveslight signals 273 in third sub-range φ₃ from optical splitter 250 andconverges light signals 273 to third exit pupil 283 at or proximate eye290. Because third virtual position 263 is spatially-separated from bothfirst virtual position 261 and second virtual position 262, third exitpupil 283 is spatially-separated from both first exit pupil 281 andsecond exit pupil 282 at or proximate eye 290.

Throughout this specification and the appended claims, reference isoften made to “points of incidence” of one or more light signal(s) at anoptical splitter. Unless the specific context requires otherwise, a“point of incidence” at an optical splitter generally refers to theposition or location on (e.g., at an outer surface of) or in (e.g.,within an inner volume of) the optical splitter at which a light signalimpinges on and/or first interacts with and/or is first influenced bythe optical splitter. For example, an optical splitter as describedherein may include one or more optical elements, such as an arrangementof optical elements, and the “point of incidence” of a light signal atthe optical splitter may refer to the position or location (e.g., thespatial “point”) at which the light signal first impinges on an opticalelement in the arrangement of optical elements. The term “point” is usedloosely in this context to refer to a general region having a particularspatial position and/or location and may include some dimensionalattribute(s) (e.g., a finite length, area, or volume) depending on thespot size and spot geometry of the light signal at the point ofincidence. In other words, the term “point” in this context is notintended to be limited to the mathematical notion of a dimensionlesspoint in space.

In the illustrated examples of FIGS. 2B, 2C, and 2D, each of sub-rangesφ₁, φ₂, and φ₃ corresponds to a respective equal portion (e.g., arespective third) of total scan range θ. Optical splitter 250 separatesor “splits” light signals 270 from the sweep of the total scan range θby SLP 220 into N=3 equal-sized sub-ranges: light signals 271 (FIG. 2B)corresponding to first sub-range φ₁=θ/3, light signals 272 (FIG. 2C)corresponding to second sub-range φ₂=θ/3, and light signals 273 (FIG.2D) corresponding to third sub-range φ₃=θ/3. That is, for a first rangeof points of incidence at optical splitter 250 corresponding to alldirections and/or angles of light signals 271 projected by SLP 220 infirst sub-range φ₁=θ/3 of the total scan range θ, at least one opticalelement of optical splitter 250 receives light signals 271 and redirects(either on its own or in combination with other optical elements) lightsignals 271 towards holographic combiner 230 effectively from firstvirtual position 261 for SLP 220; for a second range of points ofincidence at optical splitter 250 corresponding to all directions and/orangles of light signals 272 projected by SLP 220 in second sub-rangeφ₂=θ/3 of the total scan range θ, at least one optical element ofoptical splitter 250 receives light signals 272 and redirects (either onits own or in combination with other optical elements) light signals 272towards holographic combiner 230 effectively from second virtualposition 262 for SLP 220; and for a third range of points of incidenceat optical splitter 250 corresponding to all directions and/or angles oflight signals 273 projected by SLP 220 in third sub-range φ₃=θ/3 of thetotal scan range θ, at least one optical element of optical splitter 250receives light signals 273 and redirects (either on its own or incombination with other optical elements) light signals 273 towardsholographic combiner 230 effectively from third virtual position 263 forSLP 220. Each of the N=3 sub-ranges φ₁, φ₂, and φ₃ in WHUD 200corresponds to a respective equal portion (e.g., a respective third) oftotal scan range θ for illustrative purposes only. A person of skill inthe art will appreciate that alternative implementations of an opticalsplitter (and/or alternative implementations of a WHUD employing anoptical splitter) may include any number N of sub-ranges φ_(i) and thesub-ranges φ_(i) may or may not be equally-sized. At least twosub-ranges φ_(i) may be the same size and/or at least two sub-rangesφ_(i) may be different respective sizes. For example, if desired anoptical splitter with N=3 may split light signals into three sub-rangesφ₁, φ₂, and φ₃ of sizes φ₁=θ/6, φ₂=2(θ/3), and φ₃=θ/6.

As previously described, over each sub-range φ_(i) SLP 220 mayre-modulate nominally the same pattern or arrangement of light signals.An example of such is now described.

Over a sweep of the total scan range θ by SLP 220, SLP 220 may producelight signals 270. Light signals 270 may comprise first light signals271, second light signals 272, and third light signals 273.

Over first sub-range φ₁ of total scan range θ, SLP 220 may generatefirst light signals 271 and first light signals 271 may represent orembody a first set of pixels corresponding to a first image or a firstportion of an image. First light signals 271 are redirected by opticalsplitter 250 towards holographic combiner 230 along optical paths thattrace back to effectively originate from first virtual position 261 forSLP 220. Holographic combiner 230 receives first light signals 271 andconverges first light signals 271 to first exit pupil 281 at eye 290.

Over second sub-range φ₂ of total scan range θ, SLP 220 may generatesecond light signals 272 and second light signals 272 may represent orembody nominally the same first set of pixels as first light signals 271corresponding to the same first image or the same first portion of animage. Second light signals 272 are redirected by optical splitter 250towards holographic combiner 230 along optical paths that trace back toeffectively originate from second virtual position 262 for SLP 220.Holographic combiner 230 receives second light signals 272 and convergessecond light signals 272 to second exit pupil 282 at eye 290. Becausefirst light signals 271 and second light signals 272 represent or embodynominally the same display content, first exit pupil 281 and second exitpupil 282 each provides a respective instance (e.g., a respectivereplicated or repeated instance) of the same display content to adifferent respective position at or proximate eye 290. In this way, eye290 is able to see the same content regardless of which at least one offirst exit pupil 281 and/or second exit pupil 282 aligns with the gazedirection (e.g., pupil position) of eye 290. Rather than comprising asingle exit pupil at one location, eyebox 280 of WHUD 200 is expanded tocomprise spatially-separated first and second exit pupils 281 and 282.

Over third sub-range φ₃ of total scan range θ, SLP 220 may generatethird light signals 273 and third light signals 273 may represent orembody nominally the same first set of pixels as first light signals 271and second light signals 272 corresponding to the same first image orthe same first portion of an image. Third light signals 273 areredirected by optical splitter 250 towards holographic combiner 230along optical paths that trace back to effectively originate from thirdvirtual position 263 for SLP 220. Holographic combiner 230 receivesthird light signals 273 and converges third light signals 273 to thirdexit pupil 283 at eye 290. Because third light signals 273 represent orembody nominally the same display content as first light signals 271 andsecond light signals 272, third exit pupil 283 provides another instance(e.g., another replicated or repeated instance) of the same displaycontent as that provided by first exit pupil 281 and second exit pupil282 to another position at or proximate eye 290. In this way, eye 290 isable to see the same content regardless of which at least one of firstexit pupil 281, second exit pupil 282, and/or third exit pupil 283aligns with the gaze direction (e.g., pupil position) of eye 290. Eyebox280 of WHUD 200 is expanded to comprise spatially-separated first,second, and third exit pupils 281, 282, and 283. As previouslydescribed, expansion of eyebox 280 to include three exit pupils 281,282, and 283 in WHUD 200 is used for illustrative purposes only. Thepresent systems, devices, and methods may be extended to expand theeyebox of a WHUD to include any number N of exit pupils depending on therequirements of the specific application.

Throughout this specification, the expression “nominally the same” isgenerally used in reference to certain light signals (e.g., first lightsignals 271 being nominally the same as second light signals 272) toindicate that those particular light signals are defined to representthe same content when viewed by the user. For example, first lightsignals 271 and second light signals 272 are “nominally the same” whenfirst light signals 271 and second light signals 272 are both defined bySLP 220 to represent the same image, or the same portion of an image, orgenerally the same display content. The term “nominally” in “nominallythe same” is meant to reflect the fact that, in some situations, eventhough two light signals (e.g., two sets of light signals, as with firstlight signals 271 and second light signals 272) may both be defined torepresent the same display content the two light signals (or sets oflight signals) may not be identical sets of light signals. Such asituation can arise, for example, when the two light signals (e.g., thetwo sets of light signals) are each exposed to different respectiveoptical distortions.

In the various implementations described herein, multiple (i.e., N)instances of an image are effectively projected from respective ones ofmultiple (i.e., N) different virtual positions. Each one of the Nvirtual positions corresponds to a respective range of optical pathsthrough the optical splitter and effectively “projects” light signalstowards or on the holographic combiner over a respective range ofoptical paths comprising a respective range of directions and/or angles.As a consequence, each one of the N virtual positions may effectively“project” light signals with a different respective optical distortionprofile. For example, a first set of light signals (e.g., representing afirst instance of an image) effectively originating from a first virtualposition may be subject to a first set of optical distortions (e.g.,image skewing, keystoning, aberrations, and so on) resulting from theparticular set of optical paths the first set of light signals followsthrough the optical splitter, from the optical splitter to theholographic combiner, and/or from the holographic combiner to the firstexit pupil. Likewise, a second set of light signals (e.g., representinga second instance of the same image) effectively originating from asecond virtual position may be subject to a second set of opticaldistortions (e.g., image skewing, keystoning, aberrations, and so on)resulting from the particular set of optical paths the second set oflight signals follows through the optical splitter, from the opticalsplitter to the holographic combiner, and/or from the holographiccombiner to the second exit pupil. The first set of optical distortionsand the second set of optical distortions may not be identical. In orderto correct for optical distortions, the SLP may be calibrated to applyvarious offsets, compensations, corrections, or other measures toprojected light signals so that the light signals account for theoptical distortions and will appear correctly at the eye of the user.Since the first set of optical distortions and the second set of opticaldistortions may not be identical to one another, the SLP may becalibrated to apply a first image correction profile (e.g., a first setof image correction measures) to the first set of light signals (e.g.,representing the first instance of the image) and a second imagecorrection profile (e.g., a second set of image correction measures) tothe second set of light signals (e.g., representing the second instanceof the same image). Therefore, even though the first set of lightsignals and the second set of light signals may each be defined by theSLP to represent the same display content, the first set of lightsignals and the second set of light signals may not be identical to oneanother. In this example, the first set of light signals and the secondset of light signals are not the same but they are said to be “nominallythe same” because they are each defined by the SLP to represent the samedisplay content.

Returning to FIG. 2A, FIG. 2A depicts the cumulative effect of a sweepthrough successive ranges of the first sub-range φ₁ from FIG. 2B, thesecond sub-range φ₂ from FIG. 2C, and the third sub-range φ₃ from FIG.2D to produce three exit pupils 281, 282, and 283, respectively, at eye290 during a sweep of the total scan range θ by SLP 220 in accordancewith the present systems, devices, and method. In other words, FIG. 2Asimultaneously depicts each one of the three ranges of time shown inFIGS. 2B, 2C, and 2D all overlaid into one illustration. Eyebox 280comprises three exit pupils 281, 282, and 283 and each of the three exitpupils 281, 282, and 283 provides a respective temporally-separated copyor instance of the same display content to eye 290 over a differentrange of time. For example, first exit pupil 281 may provide a firstinstance of a first image to eye 290 over the range of time during whichSLP 220 sweeps through first sub-range φ₁ (e.g., over the range of timeduring which SLP 220 sweeps through the first ⅓ of the total scan rangeθ), second exit pupil 282 may provide a second instance of the firstimage to eye 290 over the range of time during which SLP 220 sweepsthrough second sub-range φ₂ (e.g., over the range of time during whichSLP 220 sweeps through the second ⅓ of the total scan range θ), andthird exit pupil 283 may provide a third instance of the first image toeye 290 over the range of time during which SLP 220 sweeps through thirdsub-range φ₃ (e.g., over the range of time during which SLP 220 sweepsthrough the third ⅓ of the total scan range θ). Thus, the threeinstances of the first image provided by respective ones of the threeexit pupils 281, 282, and 283 may be projected temporally in series(i.e., serially) with one another. In order that the user does not seethree sequential projections of the same display content, SLP 220 mayre-modulate the three respective instances of the same display contentat a rate that is too fast to be discerned by eye 290. The cumulativeeffect (i.e., the concurrence of exit pupils 281, 282, and 283) depictedin FIG. 2A may represent what is actually perceived by the user when, asdepicted sequentially in FIGS. 2B, 2C, and 2D, SLP 220 quickly (e.g., atabout 60 Hz) remodulates N sequential instances of the same displaycontent over a sweep of the total scan range θ and optical splitter 250splits the sweep of the total scan range θ into respective ones of Nsub-ranges φ_(i) with each sub-range φ_(i) corresponding to a respectiveone of the N sequential instances of the display content.

In accordance with the present systems, devices, and methods, SLP 220and optical splitter 250 together separate or “split” the light signals270 projected by SLP 220 over the total scan range θ into N=3 sub-rangesφ₁, φ₂, and φ₃ to produce N=3 instances 271, 272, and 273 of the samedisplay content. Because each of these N=3 instances follows a differentrespective range of optical paths effectively originating from adifferent respective spatially-separated virtual position 261, 262, and263 for SLP 220, holographic combiner 230 converges each of these N=3instances to a respective spatially-separated exit pupil 281, 282, and283 at or proximate eye 290. Spatially-separated exit pupils 281, 282,and 283 are distributed over an area of eye 290 that covers a widerrange of pupil positions (e.g., gaze directions) than a single exitpupil (of the same size as any one of exit pupils 281, 282, and 283) onits own. Thus, eyebox 280 is expanded by exit pupil replication in WHUD200.

In the illustrated example, each of the N=3 virtual positions 261, 262,and 263 for SLP 220 effectively created or established by opticalsplitter 250 is different (i.e., spatially-separated) from real position260. However, in some implementations optical splitter 250 may include aconfiguration or arrangement of one or more optical element(s) oroptical device(s) for which a sub-range φ_(i) of light signals 270 isdirected to holographic combiner 230 effectively from real position 260rather than from a virtual position.

In FIG. 2A, light signals 271 effectively originating from first virtualposition 261, light signals 272 effectively originating from secondvirtual position 262, and light signals 273 effectively originating fromthird virtual position 263, are all shown incident at or on about thesame region of holographic combiner 230. This configuration is exemplaryand in practice alternative configurations may be preferred depending onthe specific implementation. Generally, each sub-range φ_(i) of lightsignals (e.g., each of light signals 271, light signals 272, and lightsignals 273) may be incident upon (and received by) a respective regionor area of holographic combiner 230 and these respective areas ofholographic combiner 230 may or may not completely overlap (e.g., suchareas may partially overlap or correspond to separate, non-overlappingareas).

In a virtual retina display such as scanning laser-based WHUD 100 and/orscanning laser-based WHUD 200, there may not be an “image” formedoutside of the eye of the user. There is typically no microdisplay orprojection screen or other place where the projected image is visible toa third party; rather, the image may be formed completely within the eyeof the user. For this reason, it may be advantageous for a scanninglaser-based WHUD to be designed to accommodate the manner in which theeye forms an image.

For a light signal entering the eye (e.g., a light ray, a wavefront, anincident beam from a SLP, or similar), the eye (or more accurately, thecombination of the eye and the human brain) may determine “where” thelight signal is positioned in the user's field of view based on theregion of the retina that is illuminated by the light signal. Two lightsignals that illuminate the same region of the retina may appear in thesame position in the user's field of view. The particular region of theretina that is illuminated by any given light signal is determined bythe angle and not the location at which the light signal enters the eye.Thus, two light signals may appear in the same position in the user'sfield of view even if they enter different location of the user's pupilprovided that the two light signals have the same angle of incidencewhen they enter the user's eye. The geometry of the eye's lens is suchthat any two light signals entering the eye at the same angle,regardless of the position/location at which the light signals enter theeye, may generally be directed to the same region of the retina and somay generally appear in the same position in the user's field of view.

In at least some implementations, the scanning laser-based WHUDsdescribed herein project multiple instances of the same image onto theretina of the eye in rapid succession. Even if the multiple instancesare temporally-separated, the temporal separation may be small enough tobe undetectable by the user. If any two of the multiple instances of thesame image do not align/overlap on the eye's retina then those twoinstances of the image may not align/overlap in the user's field of viewand undesirable effects such as ghosting can occur. In order to ensurethat multiple instances of the same image (each corresponding to arespective exit pupil) align/overlap on the retina so that multipleinstances of the image align/overlap in the user's field of view, ascanning laser-based WHUD may advantageously be configured to directmultiple instances of any given light signal (each corresponding to arespective exit pupil and each representing a respective instance of thesame display content) towards the eye spatially in parallel with oneanother. More specifically and referring to FIG. 2A, the opticalsplitter 250 and/or the holographic combiner 230 may be configured,arranged and/or operated (either individually or in combination) so thatthe holographic combiner 230 redirects the N=3 sets of light signals271, 272, and 273, respectively, all spatially in parallel with oneanother towards respective regions (i.e., towards respective ones of N=3spatially-separated exit pupils 281, 282, and 283) of the eye 290 of theuser.

FIG. 2E is an illustrative diagram of WHUD 200 from FIGS. 2A, 2B, 2C,and 2D showing eyebox expansion by temporally sequential exit pupilreplication with respective instances of the same display content (e.g.,pixel(s)) projected spatially in parallel with one another towardsrespective exit pupils in accordance with the present systems, devices,and methods. In order to highlight some of the features shown in theimplementation of FIG. 2E, the corresponding aspects of FIG. 2A willfirst be noted.

In the implementation of FIG. 2A, light signals 271 effectivelyoriginating from first virtual position 261, light signals 272effectively originating from second virtual position 262, and lightsignals 273 effectively originating from third virtual position 263, allalign with one another and completely overlap on holographic combiner230. As a result, each of the N=3 exit pupils 281, 282, and 283converges at or proximate eye 290 from substantially the same area ofholographic combiner 230. Because each of the N=3 exit pupils 281, 282,and 283 originates from substantially the same area of holographiccombiner 230 but converges to a respective spatially-separated region ofeye 290, each of the N=3 exit pupils 281, 282, and 283 necessarilyincludes at least some light signals having incident angles (at eye290), or reflection angles (at holographic combiner 230), that cannot beprovided by at least one other one of the N=3 exit pupils 281, 282, and283. For example, light signals 271 (represented by lines with largedashes) that converge to exit pupil 281 include at least some angles ofincidence (at eye 290, or angles of reflection at holographic combiner230) that are not included in light signals 272 (represented by solidlines) that converge to exit pupil 282, and vice versa. As previouslydescribed, the angle of incidence of a light signal as it enters the eyedetermines where in the user's field of view the light (or the pixel ofan image embodied by the light signal) will appear. A light signalhaving an angle of incidence that is unique to one exit pupil can onlybe projected to a user when that exit pupil aligns with the user's pupil(e.g., when the user's gaze direction includes that exit pupil). Thus,when multiple spatially-separated exit pupils all originate fromsubstantially the same spatial area on holographic combiner 230, only alimited sub-region of that spatial area may be used to provide angles ofincidence that are common to all of the exit pupils and, consequently,only a respective limited fraction of the available field of view and/orresolution of each spatially-separated exit pupil may be used to provideuniform image replication across all of the exit pupils. Having lightsignals 271 effectively originating from first virtual position 261,light signals 272 effectively originating from second virtual position262, and light signals 273 effectively originating from third virtualposition 263, all align and overlap on holographic combiner 230 cansimplify some aspects of the design of optical splitter 250 and/orholographic combiner 230 but can also limit the available resolutionand/or field of view of display content that can be replicated acrossall exit pupils.

In the implementation of FIG. 2E, optical splitter 250 is modified(e.g., in geometry, orientation, and/or composition) to shift therelative trajectories of light signals 271, 272, and 273 compared totheir corresponding trajectories in the implementation of FIG. 2A. Lightsignals 271 effectively originating from first virtual position 261,light signals 272 effectively originating from second virtual position262, and light signals 273 effectively originating from third virtualposition 263, do not align or completely overlap on holographic combiner230 in FIG. 2E as they do in FIG. 2A. Instead, light signals 271, lightsignals 272, and light signals 273 are spatially distributed over thearea of holographic combiner 230 and each positioned (at incidence onholographic combiner 230) so that they are all substantially spatiallyparallel to one another when redirected (e.g., reflected) and convergedby holographic combiner 230 towards respective ones of the N=3spatially-separated exit pupils 281, 282, and 283 at or proximate eye290. That is, light signals 271 that are converged by holographiccombiner 230 to exit pupil 281, light signals 272 that are converged byholographic combiner 230 to exit pupil 282, and light signals 273 thatare converged by holographic combiner 230 to exit pupil 283, all includethe same angles of reflection from holographic combiner 230 andaccordingly the same angles of incidence with respect to eye 290. Incontrast to the implementation of FIG. 2A, in the implementation of FIG.2E none of the N=3 exit pupils 281, 282, and 283 includes a light signalhaving an angle of incidence (with respect to eye 290, or an angle ofreflection with respect to holographic combiner 230) that is not alsoincluded in each of the other ones of the N=3 exit pupils 281, 282, and283. Each of the N=3 exit pupils 281, 282, and 283 of the implementationin FIG. 2E includes the entire field of view and/or resolution availablethereto and therefore the implementation of WHUD 200 depicted in FIG. 2Ecan provide uniform image replication across multiple exit pupils (e.g.,multiple temporally-separated and spatially-separated exit pupils) withlarger field of view and/or with higher resolution than theimplementation of WHUD 200 depicted in FIG. 2A, at the cost of addedcomplexity in optical splitter 250 and/or holographic combiner 230.

As previously described, holographic combiner 230 comprises at least onehologram embedded in, encoded in, recorded in, or otherwise carried byat least one layer of holographic film. The holographic film mayinclude, as examples, a photopolymer film such as Bayfol®HX from BayerMaterialScience AG or a silver halide compound. The nature of the atleast one hologram may depend on the specific implementation.

As a first example, holographic combiner 230 may include a singlehologram that effectively operates as a fast-converging (e.g.,convergence within about 1 cm, convergence within about 2 cm, orconvergence within about 3 cm) mirror for light having the wavelength(s)provided by SLP 220. In this first example, the holographic film thatcarries the first hologram may have a relatively wide bandwidth, meaningthe hologram recorded in the holographic film may impart substantiallythe same optical effect or function on all light signals 270 projectedby SLP 220 over a relatively wide range of angles of incidence atholographic combiner 230. For the purpose of the present systems,devices, and methods, the term “wide bandwidth” in relation to hologramsand holographic films means an angular bandwidth that is greater than orequal to the total range of angles of incidence of all light signalsreceived by any given point, region, or location of the hologram orholographic film from an optical splitter. As an example, WHUD 200 mayimplement a wide bandwidth hologram in holographic combiner 230 havingan angular bandwidth of greater than or equal to about 8°. In this case,the spatial separation between virtual positions 261, 262, and 263 maybe such that any given point, region, or location of holographiccombiner 230 receives light signals (i.e., included in any of lightsignals 271, 272, and 273) spanning an 8° (or less) range of angles ofincidence at holographic combiner 230.

Consistent with conventional mirror behavior, for a singlewide-bandwidth fast-converging hologram carried by holographic combiner230 the angles of incidence for a range of light signals incident onholographic combiner 230 may influence the angles of reflection for thatrange of light signals redirected by holographic combiner 230. Sinceholographic combiner 230 is, generally during normal operation of WHUD200, fixed in place relative to SLP 220, the angles of incidence for arange of light signals are determined, at least in part, by theparticular virtual position 261, 262, or 263 for the SLP 220 from whichoptical splitter 250 causes the range of light signals to effectivelyoriginate. The spatial position of the exit pupil 281, 282, or 283 towhich the range of light signals is converged by holographic combiner230 is then determined, at least in part, by the angles of reflection ofthat range of light signals from holographic combiner 230. Each one ofvirtual positions 261, 262, and 263 provides light signals over arespective range of angles of incidence (generally but not necessarilywith at least some overlap) at holographic combiner 230 and thereforeholographic combiner 230 converges light signals from each one ofvirtual positions 261, 262, and 263 to a respective one of exit pupils281, 282, and 283. This is why, referring to FIG. 2A for example, lightsignals 271 that effectively originate from virtual position 261(represented by lines with large dashes) with a range of relativelysmall angles of incidence (compared to light signals 272 and 273 thateffectively originate from virtual positions 262 and 263, respectively)map to exit pupil 281 with a range of relatively small angles ofreflection (compared to the other exit pupils 282 and 283) and lightsignals 273 that effectively originate from virtual position 263(represented by dotted lines) with a range of relatively large angles ofincidence (compared to light signals 271 and 272 that effectivelyoriginate from virtual positions 261 and 262, respectively) map to exitpupil 283 with a range of relatively large angles of reflection(compared to the other exit pupils 281 and 282).

As a second example, rather than a single hologram, holographic combiner230 may instead include any number of multiplexed holograms. Multiplexedholograms may be advantageous when, for example, multiple wavelengths oflight signals are used (e.g., red, green, and blue light signalsgenerated by SLP 220) and/or to provide a further means to separatelight signals effectively originating from different virtual positionsfor SLP 220. The “single hologram” example described above may besuitable for an implementation in which SLP 220 only provides lightsignals of a single wavelength (e.g., only red light signals, only greenlight signals, or only blue light signals), but for implementations inwhich SLP 220 provides light signals of multiple wavelengths it may beadvantageous for holographic combiner 230 to include a respectivewavelength multiplexed hologram for each respective wavelength of lightsignals provided by SLP 220 (e.g., each respective nominal wavelength oflight signals provided by SLP 220, since a laser diode may generallyprovide light signals over a narrow waveband). Thus, when SLP 220includes three different laser diodes each providing light signals of arespective nominal wavelength (e.g., a red laser diode, a green laserdiode, and a blue laser diode) it may be advantageous for holographiccombiner 230 to include three wavelength-multiplexed holograms (e.g., ared hologram, a green hologram, and a blue hologram) each designed towork (e.g., “playback”) for light signals having a respective one of thethree nominal wavelengths. In this example, at least one “red hologram”(i.e., at least one hologram that is designed to playback for lightsignals having a wavelength that corresponds to red light) may convergea respective red component of each of light signals 271, 272, and 273 toa respective one of the N=3 exit pupils 281, 282, and 283, at least one“green hologram” (i.e., at least one hologram that is designed toplayback for light signals having a wavelength that corresponds to greenlight) may converge a respective green component of each of lightsignals 271, 272, and 273 to a respective one of the N=3 exit pupils281, 282, and 283, and at least one blue hologram (i.e., at least onehologram that is designed to playback for light signals having awavelength that corresponds to blue light) may converge a respectiveblue component of each of light signals 271, 272, and 273 to arespective one of the N=3 exit pupils 281, 282, and 283. In other words,for a light signal redirected from a particular one of the Nspatially-separated virtual positions for the SLP by the opticalsplitter, the at least one red hologram may converge a red component ofthe light signal to a particular one of the N exit pupils at orproximate the eye of the user, the at least one green hologram mayconverge a green component of the light signal to the particular one ofthe N exit pupils at or proximate the eye of the user, and the at leastone blue hologram may converge a blue component of the light signal tothe particular one of the N exit pupils at or proximate the eye of theuser.

As a third example, either apart from or in addition to multiplewavelength-multiplexed holograms, holographic combiner 230 may includeat least N angle-multiplexed holograms. That is, for an implementationwith N=3 virtual positions 261, 262 and 263 for the SLP 220 and N=3 exitpupils 281, 282, and 283, holographic combiner 230 may include at leastN=3 angle-multiplexed holograms (or N=3 sets of angle-multiplexedholograms when wavelength multiplexing is also employed, as discussedlater on). Each of the N=3 angle-multiplexed holograms may be designedto playback for light signals effectively originating from a respectiveone of the N=3 virtual positions 261, 262, and 263 for SLP 220 andconverge such light signals to a respective one of the N=3 exit pupils281, 282, and 283. That is, a first angle-multiplexed hologram may bedesigned to playback for light signals 271 effectively originating fromvirtual position 261 for SLP 220 and converge light signals 271 to firstexit pupil 281, a second angle-multiplexed hologram may be designed toplayback for light signals 272 effectively originating from virtualposition 262 for SLP 220 and converge light signals 272 to second exitpupil 282, and a third angle-multiplexed hologram may be designed toplayback for light signals 273 effectively originating from virtualposition 263 for SLP 220 and converge light signals 273 to third exitpupil 283.

For implementations that employ angle-multiplexing, it may beadvantageous for the holographic film that includes an angle-multiplexedhologram to be of relatively narrow bandwidth. Particularly, it may beadvantageous for the holographic film to have an angular bandwidth thatis less than or about equal to the minimum difference between therespective angles of incidence of two light signals that are incident onthe same point, region, or location of holographic combiner 230 buteffectively originate from different virtual positions 261, 262, and263. As an example, WHUD 200 may implement a narrow bandwidthangle-multiplexed hologram in holographic combiner 230 having an angularbandwidth of less than or equal to about 4°. In this case, thedifference between the angle of incidence (at holographic combiner 230)of a light signal 271 that effectively originates from virtual position261 and is incident at a first point on holographic combiner 230 and theangle of incidence (at holographic combiner 230) of a light signal 272that effectively originates from virtual position 262 and is incident atthe same first point on holographic combiner 230 may be less than orequal to about 4°. In this way, each respective angle-multiplexedhologram in holographic combiner 230 may be designed to substantiallyexclusively playback for a respective one of light signals 271, 272, or273 effectively originating from a respective one of virtual positions261, 262, or 263 for SLP 220 and to substantially not playback (e.g.,insubstantially playback) for the other ones of light signals 271, 272,or 273 effectively originating from the other ones of virtual positions261, 262, or 263 for SLP 220.

Generally, holographic combiner 230 may include at least N multiplexedholograms and each one of the at least N multiplexed holograms mayconverge light signals corresponding to a respective one of the Nspatially-separated virtual positions for SLP 220 to a respective one ofN exit pupils at or proximate the eye 290 of the user.

Some implementations may employ both wavelength multiplexing and anglemultiplexing. For example, an implementation that employs anglemultiplexing and light signals of multiple wavelengths (e.g., amulti-color SLP) may advantageously also employ wavelength multiplexing.In this case, holographic combiner 230 may include awavelength-multiplexed and angle-multiplexed holographic combiner thatincludes at least N angle-multiplexed red holograms, at least Nangle-multiplexed green holograms, and at least N angle-multiplexed blueholograms. Each one of the at least N angle-multiplexed red hologramsmay converge red components of light signals (e.g., 271) redirected froma respective one of the N spatially-separated virtual positions (e.g.,261) for SLP 220 by optical splitter 250 to a respective one of the Nexit pupils (e.g., 281) at or proximate eye 290. Each one of the atleast N angle-multiplexed green holograms may converge green componentsof light signals (e.g., 271) redirected from a respective one of the Nspatially-separated virtual positions (e.g., 261) for SLP 220 by opticalsplitter 250 to a respective one of the N exit pupils (e.g., 281) at orproximate eye 290. Each one of the at least N angle-multiplexed blueholograms may converge blue components of light signals (e.g., 271)redirected from a respective one of the N spatially-separated virtualpositions (e.g., 261) for SLP 220 by optical splitter 250 to arespective one of the N exit pupils (e.g., 281) at or proximate eye 290.

Implementations of holographic combiner 230 that employ multiplemultiplexed holograms may include multiple holograms in or on a singlelayer (i.e., all in or on the same layer) of holographic film or mayinclude multiple layers of holographic film with each layer ofholographic film carrying at least one respective hologram. Holographiccombiner 230 may or may not comprise at least one volumetric holographicoptical element. Generally, holographic combiner 230 may comprise asingle layer of holographic film that carries any number of holograms orholographic combiner 230 may comprise multiple layers of holographicfilm (e.g., multiple layers laminated together) with each respectivelayer of holographic film carrying any number of respective holograms.

Holographic combiner 230 may be substantially flat or planar in geometryor, as illustrated in FIGS. 2A, 2B, 2C, 2D, and 2E, holographic combiner230 may embody some curvature. In some implementations, holographiccombiner 230 may embody curvature because holographic combiner 230 iscarried by a prescription eyeglass lens 240 that has some curvature.When necessary, holographic combiner 230 may include systems, devices,and/or methods for curved holographic optical elements described in U.S.Provisional Patent Application Ser. No. 62/268,892.

The various embodiments described herein provide systems, devices, andmethods for eyebox expansion by exit pupil replication in scanninglaser-based WHUDs. Each replicated exit pupil is aligned to a respectivespatially-separated position at or proximate the eye of the user becausethe optical splitter selectively routes the light signals alongspatially-separated optical paths that each trace back to (e.g., eachappear to effectively originate from) a different spatially-separatedvirtual position for the SLP. The effect is substantially the same as ifmultiple SLPs were used instead of the optical splitter, with each SLPpositioned in a respective one of the virtual positions and with eachSLP projecting a respective instance of a light signal towards theholographic combiner; however, the use of the optical splitter hasconsiderable advantages in terms of power savings and minimizinghardware bulk.

Optical splitter 250 separates or splits light signals 270 into lightsignals 271, 272, and 273 and redirects light signals 271, 272, and 273ultimately towards respective ones of exit pupils 281, 282, and 283 ateye 290. SLP 220 may be modulated to repeat nominally the same displaycontent for each of light signals 271, 272, and 273. This redundancyenables WHUD 200 to rapidly display N=3 instances of the same image atN=3 different regions of eye 290 and thereby expand the eyebox 280 ofthe system to encompass all N=3 exit pupils 281, 282, and 283. However,in some applications or implementations, only one instance of an imagemay need to be (or want to be) displayed to eye 290 at any given time.Such can simplify the operation of SLP 220 and save the power requiredto produce multiple potentially redundant instances of the same image.In accordance with the present systems, devices, and methods, a WHUD 200may include an eye tracker communicatively coupled to SLP 220 (eitherdirectly or by common communicative coupling to another element, such asa processor or non-transitory processor-readable storage medium) todetermine the pupil position (e.g., gaze direction) of eye 290.Information about the pupil position (or gaze direction) of eye 290 maybe used by SLP 220 to determine over which one(s) of the N sub-rangesφ_(i) of the total scan range θ to modulate light signals in order toprovide display content to the user. That is, based on information aboutthe pupil position (or gaze direction) of eye 290, SLP 220 mayoptionally only generate light signals over the particular sub-range(s)φ_(i) of the total scan range θ that correspond to the particular exitpupil(s) that align(s) with the current pupil position (or gazedirection) of eye 290. If the gaze direction of eye 290 (as determinedby an eye tracker of WHUID 200) is such that the pupil of eye 290 onlyaligns with one exit pupil (e.g., with exit pupil 283), then SLP 220 maybe modulated to only generate light signals during the φ₃ sub-rangeportion of the total scan range θ so that only light signals 273 areproduced and the power associated with generating redundant lightsignals 271 and 272 may be saved.

An eye tracker included in any of the implementations of WHUDs describedherein may employ any of a variety of different eye trackingtechnologies depending on the specific implementation. For example, aneye tracker may employ any or all of the systems, devices, and methodsdescribed in U.S. Provisional Patent Application Ser. No. 62/167,767;U.S. Provisional Patent Application Ser. No. 62/271,135; U.S.Provisional Patent Application Ser. No. 62/245,792; and/or U.S.Provisional Patent Application Ser. No. 62/281,041. As previouslydescribed, WHUD 200 may include at least one processor and at least onenon-transitory processor-readable storage medium or memorycommunicatively coupled thereto. The at least one memory may storeprocessor-executable data and/or instructions that, when executed by theat least one processor, cause the at least one processor to control theoperation of either or both of SLP 220 and/or an eye tracker.

As described previously, optical splitter 250 includes at least oneoptical element that is arranged to receive light signals 270corresponding to a sweep of the total two-dimensional scan range θ bySLP 220, separate the light signals into N two-dimensional sub-rangesφ_(i) based on the point of incidence of each light signal 270 atoptical splitter 250, where

${{\sum\limits_{i = 1}^{N}\varphi_{i}} = \theta},$and redirect the light signals in each two-dimensional sub-range φ_(i)towards holographic combiner 230 effectively from a respective one of Nspatially-separated virtual positions 261, 262, and 263 for SLP 220. Asalso described previously, the total two-dimensional scan range θ of aSLP may be broken down into a total scan range Ω in a first dimensioncorresponding to all available directions and/or angles of light signalsin a first dimension (e.g., the horizontal dimension) that the SLP isoperative to output during normal use, and a total scan range ψ in asecond dimension corresponding to all available directions and/or anglesof light signals in a second dimension (e.g., the vertical dimension)that the SLP is operative to output during normal use. When the totaltwo-dimensional scan range θ of SLP 220 includes a total scan range Ω ina first dimension, then at least one optical element of optical splitter250 may be arranged to receive light signals corresponding to a sweep ofthe total scan range Ω in the first dimension by SLP 220, separate thelight signals corresponding to the sweep of the total scan range Ω inthe first dimension into X sub-ranges ω_(i) in the first dimension basedon point of incidence at optical splitter 250, where 1<X≤N and

${{\sum\limits_{i = 1}^{X}\omega_{i}} = \Omega},$and redirect the light signals corresponding to the sweep of the totalscan range Ω in the first dimension towards holographic combiner 230effectively from at least X of the N spatially-separated virtualpositions for SLP 220. In this case, each one of the X sub-ranges ω_(i)may correspond to a different one of the N spatially-separated virtualpositions for SLP 220. The particular virtual position for SLP 220 fromwhich each light signal in the sweep of the total scan range Ω in thefirst dimension is redirected by optical splitter 250 may depend on(e.g., may be determined by) the particular sub-range ω_(i) in the firstdimension to which the light signal corresponds. When holographiccombiner 230 receives light signals corresponding to the sweep of thetotal scan range Ω in the first dimension, at least one hologram ofholographic combiner 230 may converge the light signals to respectiveones of at least X of the N exit pupils at or proximate eye 290. Theparticular exit pupil towards which a light signal in the sweep of thetotal scan range Ω in the first dimension is redirected by holographiccombiner 230 may depend on (e.g., may be determined by) at least theparticular sub-range ω_(i) in the first dimension into which the lightsignal is separated by optical splitter 250.

When the total two-dimensional scan range θ of SLP 220 further includesa total scan range ψ in a second dimension, with for example θ=Ω×ψ, thenat least one optical element of optical splitter 250 may be arranged toreceive light signals corresponding to a sweep of the total scan range ψin the second dimension by SLP 220, separate the light signalscorresponding to the sweep of the total scan range ψ in the seconddimension into Y sub-ranges β_(i) in the second dimension based on pointof incidence at optical splitter 250, where 1<Y≤N and

${{\sum\limits_{i = 1}^{Y}\beta_{i}} = \Psi},$and redirect the light signals corresponding to the sweep of the totalscan range ψ in the second dimension towards holographic combiner 230effectively from at least Y of the N spatially-separated virtualpositions for SLP 220. In this case, each one of the Y sub-ranges β_(i)may correspond to a different one of the N spatially-separated virtualpositions for SLP 220. For at least one virtual position for SLP 220, atleast one of the X sub-ranges ω_(i) in the first dimension and at leastone of the Y sub-ranges β_(i) in the second dimension may bothcorrespond to the same virtual position for SLP 220. The particularvirtual position for SLP 220 from which each light signal in the sweepof the total scan range ψ in the second dimension is redirected byoptical splitter 250 may depend on (e.g., may be determined by) theparticular sub-range β_(i) in the second dimension to which the lightsignal corresponds.

When holographic combiner 230 receives light signals corresponding toboth a sweep of the total scan range Ω in the first dimension and asweep of the total scan range ψ in the second dimension, at least onehologram of holographic combiner 230 may converge the light signals tothe N exit pupils at or proximate eye 290. In this case, the particularexit pupil towards which a light signal is converged by holographiccombiner 230 may depend on (e.g., may be determined by) both theparticular sub-range ω_(i) in the first dimension and the particularsub-range β_(i) in the second dimension into which the light signal isseparated by optical splitter 250.

The illustrative examples of the present systems, devices, and methodsdepicted in FIGS. 2A, 2B, 2C, 2D, and 2E are all generally shown intwo-dimensions and generally illustrate eyebox configurations in whichmultiple exit pupils are spatially separated in one dimension across theeye of the user. In practice, the expanded eyebox configurationsdescribed herein may comprise any number N of replicated or repeatedexit pupils arranged in any two-dimensional configuration over the areaof the eye of the user. An example configuration with N=4replicated/repeated exit pupils is provided in FIG. 3.

FIG. 3 is an illustrative diagram showing an exemplary holographiccombiner 330 in two-dimensions converging four instances of replicated(e.g., repeated) light signals to form an expanded eyebox 380 comprisingfour spatially-separated exit pupils 381, 382, 383, and 384 at orproximate the eye 390 of a user in accordance with the present systems,devices, and methods. Exit pupils 381, 382, 383, and 384 are distributedover a two-dimensional area at or near eye 390 to cover a wide range ofpupil positions (e.g., gaze directions) for eye 390. As long as thepupil of eye 390 is positioned within eyebox 380, at least one of exitpupils 381, 382, 383, and 384 (in some cases a combination of at leasttwo of exit pupils 381, 382, 383, and 384) will provide light signalsthrough the pupil to eye 390 and the user will be able to see theprojected image. In terms of optical path, each one of exit pupils 381,382, 383, and 384 may receive light signals corresponding to arespective sub-range φ_(i) of the total scan range θ of an SLP.

Exemplary optical splitter 250 in FIGS. 2A, 2B, 2C, 2D, and 2E is afaceted, prismatic structure. Such a structure is shown for illustrativepurposes only and not intended to limit the composition of the opticalsplitters described herein to faceted, prismatic structures orstructures of similar geometry. While faceted, prismatic structures maybe suitable as optical splitters in certain implementations, aspreviously described the optical splitters described herein may compriseany of a variety of different components depending on the specificimplementation. Two non-limiting examples of different constructions andoperations of optical splitters as described herein are provided in FIG.4 and FIG. 5.

FIG. 4 is a schematic diagram of an example of an optical splitter 400for separating the total scan range θ of a SLP 420 into three sub-rangesφ₁, φ₂, and φ₃ in accordance with the present systems, devices, andmethods. Optical splitter 400 includes a first optical structure 450having two reflective surfaces 401 and 402 and two transmissive surfaces411 and 412. Reflective surfaces 401 and 402 are oriented at twodifferent angles. SLP 420 (which may be substantially similar to SLP 120from FIG. 1 and SLP 220 from FIGS. 2A, 2B, 2C, 2D, and 2E) has a totalscan range θ that includes sub-ranges φ₁, φ₂, and φ₃ as indicated inFIG. 4, with

${\sum\limits_{i = 1}^{3}\varphi_{i}} = {\theta.}$SLP 420 may be operated to scan three sequential copies or instances ofnominally the same image: a first instance in sub-range φ₁, a secondinstance in sub-range φ₂, and a third instance in sub-range φ₃. Thefirst instance of the image projected over sub-range φ₁ is reflected byfirst reflective surface 401 of optical structure 450 and then reflectedagain by a third reflector (e.g., mirror) 403. Third reflector 403 isoriented to redirect light signals 471 (analogous to light signals 271from FIGS. 2A, 2B, and 2E) corresponding to sub-range φ₁ towards, forexample, a projection screen or the holographic combiner of a WHUD (notshown in FIG. 4 to reduce clutter). The second instance of the imageprojected over sub-range φ₂ is transmitted through first and secondtransmissive surfaces 411 and 412 of optical structure 450 as lightsignals 472 (analogous to light signals 272 from FIGS. 2A, 2C, and 2E)corresponding to sub-range φ₂ towards, for example, a projection screenor the holographic combiner of a WHUD. The third instance of the imageprojected over sub-range φ₃ is reflected by second reflective surface402 of optical structure 450 and then reflected again by a fourthreflector (e.g., mirror) 404. Fourth reflector 404 is oriented toredirect light signals 473 (analogous to light signals 273 from FIGS.2A, 2D, and 2E) corresponding to sub-range φ₃ towards, for example, aprojection screen or the holographic combiner of a WHUD. In this way,three nominally-identical instances of an image may be produced (e.g.,sequentially generated) by SLP 420 and directed towards a holographiccombiner (e.g., 230) effectively from three different positions (onereal position, two virtual positions) for SLP 420. Depending on theposition and orientation of the holographic combiner, any two or allthree of the resulting instances of the image may overlap, or not, in avariety of different ways on the holographic combiner. In someimplementations, the area of the holographic combiner where all threeimages completely overlap may be advantageously used, during operation,as a primary field of view.

Optical splitter 400 represents an example of a configuration of anoptical splitter that may be used in conjunction with an accordinglyadapted SLP operational mode in order to expand the eyebox of a retinalscanning display system by exit pupil replication.

FIG. 5 is an illustrative diagram of an example of an optical splitter550 for separating the total two-dimensional scan range θ of a SLP 520into four two-dimensional sub-ranges φ₁, φ₂, φ₃, and φ₄ in accordancewith the present systems, devices, and methods. Optical splitter 550 isa faceted, prismatic optical device or structure (similar to opticalsplitter 250 from FIGS. 2A, 2B, 2C, 2D, and 2E) with various surfacesarranged to reflect, refract, diffract, and/or generally influence theoptical path of light signals 570 generated by SLP 520 and incidentthereon or therein. Optical splitter 550 is a single, solid opticalstructure formed out of a conventional optic material such as a plastic,glass, or fluorite, though in alternative implementations opticalsplitter 550 may comprise a contiguous or otherwise mated combination ofseparate optical structures. Various facets 501 (collectively, only onecalled out to reduce clutter) of optical splitter 550 are arranged todefine distinct input regions (corresponding to specific sub-rangesφ_(i) of the total scan range θ of SLP 520 and with specific ranges ofpoints of incidence on optical splitter 550) and/or output regions (eachrespectively corresponding to all optical paths that trace back to arespective one of N=4 virtual positions 561, 562, 563, and 564 for SLP520). In order to align with and deliberately redirect light signals 570from SLP 520, the various facets 501 of optical splitter 550 arearranged at different angles relative to the input and output opticalpaths of light signals 570 and relative to any or all of the length,width, and/or depth of optical splitter 550. Generally, optical splitter550 is a faceted optical structure with at least N=4 facets 501. Atleast one respective facet 501 corresponds to each respective one of theN=4 spatially-separated virtual positions 561, 562, 563, and 564 for SLP520.

FIG. 5 shows that the total two-dimensional scan range θ of SLP 520comprises a total scan range Ω in a first (e.g., horizontal) dimensionand a total scan range ψ in a second (e.g., vertical) dimension, withθ=Ω×ψ. SLP 520 is located at real position 560. For a sweep of the totaltwo-dimensional scan range θ of SLP 520, optical splitter 550 (e.g.,various external and our internal surfaces and/or facets 501 thereof)receives light signals 570 from SLP 520 at real position 560, splitslight signals 570 into four two-dimensional sub-ranges φ₁, φ₂, φ₃, andφ₄, and redirects light signals 570 so that each two-dimensionalsub-range φ₁, φ₂, φ₃, and φ₄ appears to effectively originate from arespective spatially-separated virtual position 561, 562, 563, and 564for SLP 520. Virtual positions 561, 562, 563, and 564 arespatially-separated over at least two spatial dimensions (e.g., over twoor three spatial dimensions). The particular two-dimensional sub-rangeφ_(i) into which optical splitter 550 splits any given light signal 570depends on (e.g., is determined by) the particular point of incidence ofthat light signal at or on optical splitter 550. Thus, for a sweep ofthe total two-dimensional scan range θ of SLP 520, optical splitter 550redirects first sub-range φ₁ of light signals 570 that are incidenttherein or thereon over a first range of points of incidence (e.g., overa first facet 501 of optical splitter 550 that aligns with the firstrange of points of incidence) to effectively originate from firstvirtual position 561, optical splitter 550 redirects second sub-range φ₂of light signals 570 that are incident therein or thereon over a secondrange of points of incidence (e.g., over a second facet 501 of opticalsplitter 550 that aligns with the second range of points of incidence)to effectively originate from second virtual position 562, opticalsplitter 550 redirects third sub-range φ₃ of light signals 570 that areincident therein or thereon over a third range of points of incidence(e.g., over a third facet 501 of optical splitter 550 that aligns withthe third range of points of incidence) to effectively originate fromthird virtual position 563, and optical splitter 550 redirects fourthsub-range φ₄ of light signals 570 that are incident therein or thereonover a fourth range of points of incidence (e.g., over a fourth facet501 of optical splitter 550 that aligns with the fourth range of pointsof incidence) to effectively originate from fourth virtual position 564.The respective first, second, third, and fourth facets 501 describedabove may be located at or on an input surface (i.e., at or on thereceiving side) of optical splitter 550, or in an internal volume ofoptical splitter 550, or at or on an output surface (i.e., at or on theredirecting side) of optical splitter 550. In some implementations, therespective first, second, third, and fourth facets 501 described abovemay be located at or on an input surface (i.e., at or on the receivingside) of optical splitter or within an internal volume of opticalsplitter and each of the first, second, third, and fourth facets 501described may have a corresponding paired facet (e.g., a fifth facet, asixth facet, a seventh facet, and an eighth facet) located at or on theoutput surface (i.e., at or on the redirecting side) of optical splitter550.

Because the total two-dimensional scan range θ of SLP 520 comprises atotal scan range Ω in a first (e.g., horizontal) dimension and a totalscan range ψ in a second (e.g., vertical) dimension, each respectivetwo-dimensional sub-range φ₁, φ₂, φ₃, and φ₄ comprises a respectivecombination of a sub-range ω_(i) in the first dimension and a sub-rangeβ_(i) in the second dimension. Specifically, first two-dimensionalsub-range φ₁ comprises a first sub-range ω₁ in the first dimension and afirst sub-range β₁ in the second dimension such that φ₁=ω₁×β₁, secondtwo-dimensional sub-range φ₂ comprises a second sub-range ω₂ in thefirst dimension and the first sub-range β₁ in the second dimension suchthat φ₂=ω₂×β₁, third two-dimensional sub-range φ₃ comprises the firstsub-range ω₁ in the first dimension and a second sub-range β₂ in thesecond dimension such that φ₃=ω₁×β₂, and fourth two-dimensionalsub-range φ₄ comprises the second sub-range ω₂ in the first dimensionand the second sub-range β₂ in the second dimension such that φ₄=ω₂×β₂.For a rectangular or grid-like arrangement of sub-ranges φ_(i), when thetotal two-dimensional scan range θ of SLP 520 comprises a total scanrange Ω in a first dimension and a total scan range ψ in a seconddimension with θ=Ω×ψ, the number of two-dimensional sub-ranges φ_(i) maybe equal to at least the number of sub-ranges ω_(i) in the firstdimension multiplied by the number of sub-ranges β_(i) in the seconddimension. However, in other implementations a non-rectangulararrangement of sub-ranges φ_(i), such as a triangular, circular,polygonal, or amorphous arrangement of sub-ranges φ_(i), may beemployed.

In addition to various WHUD systems and devices that provide eyeboxexpansion by exit pupil replication (e.g., exit pupil repetition), thevarious embodiments described herein also include methods of expandingthe eyebox of a WHUD by exit pupil replication.

FIG. 6 is a flow-diagram showing a method 600 of operating a WHUD inaccordance with the present systems, devices, and methods. The WHUD maybe substantially similar to WHUD 100 or WHUD 200 and generally includesa SLP, an optical splitter, and a holographic combiner. Method 600includes four acts 601, 602, 603, and 604, though those of skill in theart will appreciate that in alternative embodiments certain acts may beomitted and/or additional acts may be added. Those of skill in the artwill also appreciate that the illustrated order of the acts is shown forexemplary purposes only and may change in alternative embodiments. Forthe purpose of method 600, the term “user” refers to a person that iswearing the WHUD.

At 601, an SLP of the WHUD generates a first light signal. The firstlight signal may represent a first instance of an image or a firstinstance of a portion of an image. For example, the first light signalmay represent a first instance of one or more pixel(s) of an image.

At 602, the optical splitter receives the first light signal at a firstpoint of incidence thereon or therein (e.g., at or on an outer surfaceof the optical splitter or within an inner volume of the opticalsplitter). Depending on the specific design of the optical splitter inthe specific implementation of method 600, the first point of incidencemay or may not correspond to a first one of multiple available opticalelements (or a first facet of multiple available facets) that make upthe optical splitter.

At 603, the optical splitter redirects the first light signal towardsthe holographic combiner effectively from a first one of Nspatially-separated virtual positions for the SLP, where N is an integergreater than 1. The first virtual position for the SLP from which theoptical splitter redirects the first light signal may depend on (e.g.,may be determined by or in part by) the first point of incidence atwhich the optical splitter receives the first light signal at 602.

At 604, the holographic combiner redirects the first light signaltowards the eye of the user. In particular, the holographic combiner mayconverge the first light signal to a first one of N exit pupils at orproximate the eye of the user. The first exit pupil to which theholographic combiner converges the first light signal may depend on(e.g., may be determined by) the first virtual position for the SLP fromwhich the optical splitter redirects the first light signal at 603.

In some implementations, the holographic combiner may include a singlehologram that converges the first light signal to a first one of N exitpupils at the eye of the user based on the angle of incidence of thefirst light signal at the particular point or region of the holographiccombiner at which the first light signal is received (as determined by,e.g., the first virtual position for the SLP from which the opticalsplitter redirects the first light signal at 603). Even in suchimplementations, the holographic combiner may comprise at least twowavelength multiplexed holograms to respectively playback for (e.g.,perform the redirecting and/or converging of act 604) at least twocomponents of the first light signal having different wavelengths, suchas at least two color components of the first light signal. For example,the SLP may comprise a red laser diode, a green laser diode, and a bluelaser diode and the first light signal may comprise a red component, agreen component, and a blue component. In this case, the holographiccombiner may comprise a red hologram, a green hologram, and a bluehologram and: the red hologram may converge a red component of the firstlight signal to the first exit pupil at or proximate the eye of theuser, the green hologram may converge a green component of the firstlight signal to the first exit pupil at or proximate the eye of theuser, and the blue hologram may converge a blue component of the firstlight signal to the first exit pupil at or proximate the eye of theuser.

In some implementations, the holographic combiner may include Nangle-multiplexed red holograms, N angle-multiplexed green holograms,and N angle-multiplexed blue holograms. In this case, a first one of theN angle-multiplexed red holograms may converge the red component of thefirst light signal to the first exit pupil, a first one of the Nangle-multiplexed green holograms may converge the green component ofthe first light signal to the first exit pupil, and a first one of the Nangle-multiplexed blue holograms may converge the blue component of thefirst light signal to the first exit pupil. The particular ones of the Nangle-multiplexed red holograms, the N angle-multiplexed greenholograms, and the N angle-multiplexed blue holograms may depend on(e.g., may be determined by) the first virtual position for the SLP fromwhich the optical splitter redirects the first light signal at 603.

Method 600 may be extended in various ways. For example, the SLP maygenerate at least a second light signal, the optical splitter mayreceive the second light signal at a second point of incidence andredirect the second light signal towards the holographic combinereffectively from a second one of the N spatially-separated virtualpositions for the SLP, and the holographic combiner may converge thesecond light signal to a second one of the N exit pupils at or proximatethe eye of the user. The second virtual position for the SLP from whichthe optical splitter redirects the second light signal depends on (e.g.,may be determined by) the second point of incidence at which the opticalsplitter receives the second light signal. When the SLP has a total scanrange θ, the optical splitter may receive the first light signal (at602) at a first point of incidence that is included in a first one φ₁ ofN sub-ranges φ_(i) of the total scan range θ for the SLP, where

${\sum\limits_{i = 1}^{N}\varphi_{i}} = {\theta.}$In this case, the first one of N spatially-separated virtual positionsfor the SLP from which the optical splitter redirects the first lightsignal at 603 may depend on (e.g., may be determined by) the firstsub-range φ₁ of the total scan range θ for the SLP. Similarly, theoptical splitter may receive the second light signal at a second pointof incidence that is included in a second one φ₂ of the N sub-rangesφ_(i) of the total scan range θ for the SLP and the second one of Nspatially-separated virtual positions for the SLP from which the opticalsplitter redirects the second light signal may depend on (e.g., may bedetermined by) the second sub-range φ₂ of the total scan range θ for theSLP.

FIG. 7 is a flow-diagram showing a method 700 of operating a WHUD inaccordance with the present systems, devices, and methods. The WHUD maybe substantially similar to WHUD 100 or WHUD 200 and generally includesa SLP, an optical splitter, and a holographic combiner. Method 700includes five acts 701, 702, 703, 704, and 705, though those of skill inthe art will appreciate that in alternative embodiments certain acts maybe omitted and/or additional acts may be added. Those of skill in theart will also appreciate that the illustrated order of the acts is shownfor exemplary purposes only and may change in alternative embodiments.For the purpose of method 700, the term “user” refers to a person thatis wearing the WHUD.

At 701, the SLP generates light signals corresponding to a sweep of thetotal two-dimensional scan range θ for the SLP. Depending on thespecific implementation, the SLP may sweep a total scan range Ω in afirst dimension at each discrete step along a sweep of a total scanrange ψ in a second dimension in order to sweep the totaltwo-dimensional scan range θ.

At 702, the optical splitter receives the light signals corresponding tothe sweep of the total two-dimensional scan range θ by the SLP at 701.The total two-dimensional scan range θ of the SLP may comprise Ntwo-dimensional sub-ranges φ_(i) where N is an integer greater than 1and

${\sum\limits_{i = 1}^{N}\varphi_{i}} = {\theta.}$Each two-dimensional sub-range φ_(i) may comprise a respectivecombination of a sub-range ω_(i) in the first dimension and a sub-rangeβ_(i) in the second dimension. The optical splitter may be positioned,oriented, and/or generally arranged so that each two-dimensionalsub-range φ_(i) corresponds to light signals having a respective rangeof points of incidence at or on the optical splitter.

At 703, the optical splitter splits, divides, furcates, branches, orgenerally “separates” the light signals into the N two-dimensionalsub-ranges φ_(i) based on the point of incidence at which each lightsignal is received by the optical splitter at 702.

At 704, the optical splitter redirects the light signals towards theholographic combiner. The optical splitter may redirect each lightsignal effectively from a particular one of N spatially-separatedvirtual positions for the SLP, with the particular virtual position forany given light signal dependent on (e.g., determined by) the particulartwo-dimensional sub-range φ_(i) to which the light signal corresponds.

At 705, the holographic combiner converges each light signal to one of Nexit pupils at or proximate the eye of the user. The particular one ofthe N exit pupils to which the holographic combiner converges a lightsignal may depend on (e.g., may be determined by) the particulartwo-dimensional sub-range φ_(i) into which the optical splitterseparates the light signal at 703. As previously described, theholographic combiner may comprise any number of holograms including, insome implementations, at least N multiplexed holograms. When theholographic combiner includes at least N multiplexed holograms, each oneof the at least N multiplexed holograms may converge light signals toone of the N exit pupils.

In accordance with the present systems, devices, and methods, the eyeboxof a retina-scanning projector may be expanded by replication of one ormore exit pupils. In this approach, a given exit pupil may have adefined size that is about equal to or smaller than the diameter of theeye's pupil, such as about 4 mm or less (e.g., about 2 mm), so that alllight from an image enters the eye when the exit pupil impinges on(e.g., aligns with or overlies) the user's (physical) pupil. However,when the user moves their eye, alignment between the exit pupil and theuser's pupil may be lost and the projected image may disappear from theuser's field of view. Thus, in the “eyebox expansion through exit pupilreplication” approaches described herein, multiple exit pupils may beprojected and tiled over the user's eye so that at least one exit pupilaligns with the user's eye for multiple, many, most, or all eyepositions.

Throughout this specification and the appended claims, the term “about”is sometimes used in relation to specific values or quantities. Forexample, fast-convergence within “about 2 cm.” Unless the specificcontext requires otherwise, the term about generally means±15%.

The “optical splitter” described herein is an optical device. A firstnon-limiting example of an optical splitter comprising an arrangement ofreflectors is illustrated in (and described with reference to) FIG. 4and a second non-limiting example of an optical comprising a faceted,prismatic optical device is illustrated (and described with referenceto) FIG. 5; however, the present systems, devices, and methods are notintended to be limited to the exemplary implementations of opticalsplitters from FIGS. 4 and 5. An optical splitter as described hereinmay comprise any number and/or arrangement of optical elements and/oroptical devices (including passive or static elements and active ordynamic (e.g., actuatable) elements), such as mirrors, lenses,diffraction gratings, beam-splitters, prisms, half-silvered surfaces,dichroics, dielectric coatings, and/or any other optical device(s) thata person of skill in the art would employ to split the light signal orimage as described herein. A person of skill in the art will appreciatethat the optical splitter described herein may employ any one or more ofa wide range of different optical device(s), individually or incombination, depending on the requirements of the specificimplementation. Accordingly, the present systems, devices, and methodsare representative implementations in which an optical device orarrangement of optical devices optically splits the light signal orimage described herein.

A person of skill in the art will appreciate that the present systems,devices, and methods may be applied or otherwise incorporated into WHUDarchitectures that employ one or more light source(s) other than a SLP.For example, in some implementations the SLP described herein may bereplaced by another light source, such as a light source comprising oneor more light-emitting diodes (“LEDs”), one or more organic LEDs(“OLEDs”), one or more digital light processors (“DLPs”). Such non-laserimplementations may advantageously employ additional optics tocollimate, focus, and/or otherwise direct projected light signals.Unless the specific context requires otherwise, a person of skill in theart will appreciate that references to a “SLP” throughout the presentsystems, devices, and methods are representative and that other lightsources (combined with other optics, as necessary) may be applied oradapted to serve the same general purpose as the SLPs described herein.

A person of skill in the art will appreciate that the present systems,devices, and methods may be applied or otherwise incorporated into WHUDarchitectures that employ one or more transparent combiner(s) other thana holographic combiner. For example, in some implementations theholographic combiner described herein may be replaced by anon-holographic device that serves substantially the same generalpurpose, such as prismatic film, a film that carries a microlens array,and/or a waveguide structure. Such non-holographic implementations mayor may not employ additional optics. Unless the specific contextrequires otherwise, a person of skill in the art will appreciate thatreferences to a “holographic combiner” throughout the present systems,devices, and methods are representative and that other transparentcombiners (combined with other optics, as necessary) may be applied oradapted for application to serve the same general purpose as theholographic combiners described herein.

A person of skill in the art will appreciate that the variousembodiments for eyebox expansion by exit pupil replication describedherein may be applied in non-WHUD applications. For example, the presentsystems, devices, and methods may be applied in non-wearable heads-updisplays and/or in other projection displays, including virtual realitydisplays, in which the holographic combiner need not necessarily betransparent.

In binocular implementations (i.e., implementations in which displaycontent is projected into both eyes of the user), the total field ofview may be increased by deliberately projecting a different field ofview to each eye of the user. The two fields of view may overlap, sothat both eyes see content at the center of the field of view while theleft eye sees more content at the left of the field of view and theright eye sees more content at the right of the field of view.

In some implementations that employ multiple exit pupils, all exitpupils may optionally be active at all times (allowing for temporalseparation). Alternatively, implementations that also employeye-tracking, may activate only the exit pupil that corresponds to wherethe user is looking (based on eye-tracking) while one or more exitpupil(s) that is/are outside of the user's field of view may bedeactivated.

In some implementations, the scan range of the projector can be activelychanged to increase resolution in the direction the eye is looking or inthe occupied exit pupil. Such is an example of heterogeneous imageresolution as described in U.S. Provisional Patent Application Ser. No.62/134,347.

Eyebox expansion may advantageously enable a user to see displayedcontent while gazing in a wide range of directions. Furthermore, eyeboxexpansion may also enable a wider variety of users having a wider rangeof eye arrangements to adequately see displayed content via a givenWHUD. Anatomical details such as interpupillary distance, eye shape,relative eye positions, and so on can all vary from user to user. Thevarious eyebox expansion methods described herein may be used to rendera WHUD more robust over (and therefore more usable by) a wide variety ofusers having anatomical differences. In order to even furtheraccommodate physical variations from user to user, the various WHUDsdescribed herein may include one or more mechanical structure(s) thatenable the user to controllably adjust the physical position and/oralignment of one or more exit pupil(s) relative to their own eye(s).Such mechanical structures may include one or more hinge(s), dial(s),flexure(s), tongue and groove or other slidably-coupled components, andthe like. For example, at least one of the SLP and/or the opticalsplitter may be physically movable and/or rotatable on the supportstructure and the user may physically move and/or rotate the SLP and/orthe optical splitter to change a position of at least one of the N exitpupils relative to the eye. Alternatively, the approaches taught hereinmay advantageously avoid the need for inclusion of such additionalmechanical structures, allowing a smaller package and less weight thanmight otherwise be obtainable.

In some implementations, one or more optical fiber(s) may be used toguide light signals along some of the paths illustrated herein.

The various implementations described herein may, optionally, employ thesystems, devices, and methods for preventing eyebox degradationdescribed in U.S. Provisional Patent Application Ser. No. 62/288,947.

The WHUDs described herein may include one or more sensor(s) (e.g.,microphone, camera, thermometer, compass, and/or others) for collectingdata from the user's environment. For example, one or more camera(s) maybe used to provide feedback to the processor of the WHUD and influencewhere on the display(s) any given image should be displayed.

The WHUDs described herein may include one or more on-board powersources (e.g., one or more battery(ies)), a wireless transceiver forsending/receiving wireless communications, and/or a tethered connectorport for coupling to a computer and/or charging the one or more on-boardpower source(s).

The WHUDs described herein may receive and respond to commands from theuser in one or more of a variety of ways, including without limitation:voice commands through a microphone; touch commands through buttons,switches, or a touch sensitive surface; and/or gesture-based commandsthrough gesture detection systems as described in, for example, U.S.Non-Provisional patent application Ser. No. 14/155,087, U.S.Non-Provisional patent application Ser. No. 14/155,107, PCT PatentApplication PCT/US2014/057029, and/or U.S. Provisional PatentApplication Ser. No. 62/236,060, all of which are incorporated byreference herein in their entirety.

The various implementations of WHUDs described herein may include any orall of the technologies described in U.S. Provisional Patent ApplicationSer. No. 62/117,316, U.S. Provisional Patent Application Ser. No.62/156,736, and/or U.S. Provisional Patent Application Ser. No.62/242,844.

Throughout this specification and the appended claims the term“communicative” as in “communicative pathway,” “communicative coupling,”and in variants such as “communicatively coupled,” is generally used torefer to any engineered arrangement for transferring and/or exchanginginformation. Exemplary communicative pathways include, but are notlimited to, electrically conductive pathways (e.g., electricallyconductive wires, electrically conductive traces), magnetic pathways(e.g., magnetic media), and/or optical pathways (e.g., optical fiber),and exemplary communicative couplings include, but are not limited to,electrical couplings, magnetic couplings, and/or optical couplings.

Throughout this specification and the appended claims, infinitive verbforms are often used. Examples include, without limitation: “to detect,”“to provide,” “to transmit,” “to communicate,” “to process,” “to route,”and the like. Unless the specific context requires otherwise, suchinfinitive verb forms are used in an open, inclusive sense, that is as“to, at least, detect,” to, at least, provide,” “to, at least,transmit,” and so on.

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to other portable and/or wearableelectronic devices, not necessarily the exemplary wearable electronicdevices generally described above.

For instance, the foregoing detailed description has set forth variousembodiments of the devices and/or processes via the use of blockdiagrams, schematics, and examples. Insofar as such block diagrams,schematics, and examples contain one or more functions and/oroperations, it will be understood by those skilled in the art that eachfunction and/or operation within such block diagrams, flowcharts, orexamples can be implemented, individually and/or collectively, by a widerange of hardware, software, firmware, or virtually any combinationthereof. In one embodiment, the present subject matter may beimplemented via Application Specific Integrated Circuits (ASICs).However, those skilled in the art will recognize that the embodimentsdisclosed herein, in whole or in part, can be equivalently implementedin standard integrated circuits, as one or more computer programsexecuted by one or more computers (e.g., as one or more programs runningon one or more computer systems), as one or more programs executed by onone or more controllers (e.g., microcontrollers) as one or more programsexecuted by one or more processors (e.g., microprocessors, centralprocessing units, graphical processing units), as firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of ordinary skill in the art in light of theteachings of this disclosure.

When logic is implemented as software and stored in memory, logic orinformation can be stored on any processor-readable medium for use by orin connection with any processor-related system or method. In thecontext of this disclosure, a memory is a processor-readable medium thatis an electronic, magnetic, optical, or other physical device or meansthat contains or stores a computer and/or processor program. Logicand/or the information can be embodied in any processor-readable mediumfor use by or in connection with an instruction execution system,apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions associated with logic and/or information.

In the context of this specification, a “non-transitoryprocessor-readable medium” can be any element that can store the programassociated with logic and/or information for use by or in connectionwith the instruction execution system, apparatus, and/or device. Theprocessor-readable medium can be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus or device. More specific examples (anon-exhaustive list) of the computer readable medium would include thefollowing: a portable computer diskette (magnetic, compact flash card,secure digital, or the like), a random access memory (RAM), a read-onlymemory (ROM), an erasable programmable read-only memory (EPROM, EEPROM,or Flash memory), a portable compact disc read-only memory (CDROM),digital tape, and other non-transitory media.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, all of the U.S. patents,U.S. patent application publications, U.S. patent applications, foreignpatents, foreign patent applications and non-patent publicationsreferred to in this specification and/or listed in the Application DataSheet which are owned by Thalmic Labs Inc., including but not limitedto: U.S. Provisional Patent Application Ser. No. 62/214,600, U.S.Provisional Patent Application Ser. No. 62/268,892, U.S. ProvisionalPatent Application Ser. No. 62/167,767, U.S. Provisional PatentApplication Ser. No. 62/271,135, U.S. Provisional Patent ApplicationSer. No. 62/245,792, U.S. Provisional Patent Application Ser. No.62/281,041, U.S. Provisional Patent Application Ser. No. 62/134,347,U.S. Provisional Patent Application Ser. No. 62/288,947, U.S.Non-Provisional patent application Ser. No. 14/155,087, U.S.Non-Provisional patent application Ser. No. 14/155,107, PCT PatentApplication PCT/US2014/057029, U.S. Provisional Patent Application Ser.No. 62/236,060, U.S. Provisional Patent Application Ser. No. 62/117,316,U.S. Provisional Patent Application Ser. No. 62/156,736, and U.S.Provisional Patent Application Ser. No. 62/242,844, are incorporatedherein by reference, in their entirety. Aspects of the embodiments canbe modified, if necessary, to employ systems, circuits and concepts ofthe various patents, applications and publications to provide yetfurther embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A wearable heads-up display comprising: asupport structure that in use is worn on a head of a user; a scanninglaser projector carried by the support structure, wherein the scanninglaser projector has a total scan range Ω in a first dimension, where0°<Ω<180°; a holographic combiner carried by the support structure,wherein the holographic combiner is positioned within a field of view ofan eye of the user when the support structure is worn on the head of theuser; and an optical splitter carried by the support structure andpositioned in an optical path between the scanning laser projector andthe holographic combiner, the optical splitter comprising at least oneoptical element arranged to receive light signals generated by thescanning laser projector and redirect each light signal towards theholographic combiner effectively from one of N spatially-separatedvirtual positions for the scanning laser projector, where N is aninteger greater than 1, the particular virtual position for the scanninglaser projector from which a light signal is redirected by the opticalsplitter determined by a point of incidence at which the light signal isreceived by the optical splitter, wherein at least one optical elementof the optical splitter is arranged to separate the total scan range Ωof the scanning laser projector in the first dimension into X sub-rangesω_(i) in the first dimension, where 1<X≤N and${{\sum\limits_{i = 1}^{X}\omega_{i}} = \Omega},$ and wherein each oneof the X sub-ranges ω_(i) corresponds to a different one of the Nspatially-separated virtual positions for the scanning laser projector,and wherein the holographic combiner comprises at least one hologrampositioned and oriented to redirect the light signals towards the eye ofthe user.
 2. The wearable heads-up display of claim 1 wherein thescanning laser projector has a total two-dimensional scan range θ and atleast one optical element of the optical splitter is arranged toseparate the total two-dimensional scan range θ of the scanning laserprojector into N two-dimensional sub-ranges φ_(i), where${{\sum\limits_{i = 1}^{N}\varphi_{i}} = \theta},$ and wherein each oneof the N sub-ranges φ_(i) corresponds to a respective one of the Nspatially-separated virtual positions for the scanning laser projector.3. The wearable heads-up display of claim 2 wherein at least one opticalelement of the optical splitter is arranged to: receive light signalscorresponding to a sweep of the total two-dimensional scan range θ bythe scanning laser projector; separate the light signals correspondingto the sweep of the total two-dimensional scan range θ into the Ntwo-dimensional sub-ranges (p, based on point of incidence at theoptical splitter; and redirect the light signals corresponding to thesweep of the total two-dimensional scan range θ towards the holographiccombiner effectively from each of the N spatially-separated virtualpositions for the scanning laser projector, the particular virtualposition for the scanning laser projector from which each light signalin the sweep of the total two-dimensional scan range θ is redirected bythe optical splitter determined by the particular two-dimensionalsub-range φ_(i) to which the light signal corresponds.
 4. The wearableheads-up display of claim 1 wherein at least one optical element of theoptical splitter is arranged to: receive light signals corresponding toa sweep of the total scan range Ω in the first dimension by the scanninglaser projector; separate the light signals corresponding to the sweepof the total scan range Ω in the first dimension into the X sub-rangescoin the first dimension based on point of incidence at the opticalsplitter; and redirect the light signals corresponding to the sweep ofthe total scan range Ω in the first dimension towards the holographiccombiner effectively from at least X of the N spatially-separatedvirtual positions for the scanning laser projector, the particularvirtual position for the scanning laser projector from which each lightsignal in the sweep of the total scan range Ω in the first dimension isredirected by the optical splitter determined by the particularsub-range ω_(i) in the first dimension to which the light signalcorresponds.
 5. The wearable heads-up display of claim 1 wherein thescanning laser projector has a total scan range ψ in a second dimension,where 0°<ψ<180°, and at least one optical element of the opticalsplitter is arranged to separate the total scan range ψ of the scanninglaser projector in the second dimension into Y sub-ranges β_(i) in thesecond dimension, where 1<Y≤N and${{\sum\limits_{i = 1}^{Y}\beta_{i}} = \Psi},$ and wherein each one ofthe Y sub-ranges β_(i) corresponds to a different one of the Nspatially-separated virtual positions for the scanning laser projector.6. The wearable heads-up display of claim 5 wherein at least one opticalelement of the optical splitter is arranged to: receive light signalscorresponding to a sweep of the total scan range ψ in the seconddimension by the scanning laser projector; separate the light signalscorresponding to the sweep of the total scan range ψ in the seconddimension into the Y sub-ranges β_(i) in the second dimension based onpoint of incidence at the optical splitter; and redirect the lightsignals corresponding to the sweep of the total scan range ψ in thesecond dimension towards the holographic combiner effectively from atleast Y of the N spatially-separated virtual positions for the scanninglaser projector, the particular virtual position for the scanning laserprojector from which a light signal in the sweep of the total scan rangeψ in the second dimension is redirected by the optical splitterdetermined by the particular sub-range β_(i) in the second dimension towhich the light signal corresponds.
 7. The wearable heads-up display ofclaim 1 wherein the support structure has a general shape and appearanceof an eyeglasses frame.
 8. The wearable heads-up display of claim 7,further comprising a prescription eyeglass lens, wherein the holographiccombiner is carried by the prescription eyeglass lens.
 9. The wearableheads-up display of claim 1 wherein the at least one hologram of theholographic combiner converges light signals to respective ones of Nexit pupils at or proximate the eye of the user, the particular exitpupil determined by the particular virtual position for the scanninglaser projector from which a light signal is redirected by the opticalsplitter.
 10. The wearable heads-up display of claim 9 wherein theholographic combiner includes at least N multiplexed holograms, andwherein each one of the at least N multiplexed holograms converges lightsignals corresponding to a respective one of the N spatially-separatedvirtual positions for the scanning laser projector to a respective oneof the N exit pupils at or proximate the eye of the user.
 11. Thewearable heads-up display of claim 9 wherein: the scanning laserprojector includes a red laser diode, a green laser diode, and a bluelaser diode; and the holographic combiner includes awavelength-multiplexed holographic combiner that includes at least onered hologram, at least one green hologram, and at least one bluehologram, and wherein for a light signal redirected from a particularone of the N spatially-separated virtual positions for the scanninglaser projector by the optical splitter, the at least one red hologramconverges a red component of the light signal to a particular one of theN exit pupils at or proximate the eye of the user, the at least onegreen hologram converges a green component of the light signal to theparticular one of the N exit pupils at or proximate the eye of the user,and the at least one blue hologram converges a blue component of thelight signal to the particular one of the N exit pupils at or proximatethe eye of the user.
 12. The wearable heads-up display of claim 11wherein the holographic combiner includes a wavelength-multiplexed andangle-multiplexed holographic combiner that includes at least Nangle-multiplexed red holograms, at least N angle-multiplexed greenholograms, and at least N angle-multiplexed blue holograms, and whereineach one of the at least N angle-multiplexed red holograms converges redcomponents of light signals redirected from a respective one of the Nspatially-separated virtual positions for the scanning laser projectorby the optical splitter to a respective one of the N exit pupils at orproximate the eye of the user, each one of the at least Nangle-multiplexed green holograms converges green components of lightsignals redirected from a respective one of the N spatially-separatedvirtual positions for the scanning laser projector by the opticalsplitter to a respective one of the N exit pupils at or proximate theeye of the user, and each one of the at least N angle-multiplexed blueholograms converges blue components of light signals redirected from arespective one of the N spatially-separated virtual positions for thescanning laser projector by the optical splitter to a respective one ofthe N exit pupils at or proximate the eye of the user.
 13. The wearableheads-up display of claim 9 wherein at least one of the scanning laserprojector and/or the optical splitter is physically movable and/orrotatable on the support structure, and wherein physical movement and/orrotation of the scanning laser projector and/or optical splitter changesa position of at least one of the N exit pupils relative to the eye ofthe user.
 14. The wearable heads-up display of claim 1 wherein the lightsignal includes an image comprising at least two pixels.
 15. Thewearable heads-up display of claim 1 wherein at least one opticalelement of the optical splitter is arranged to receive N light signalsgenerated by the scanning laser projector and redirect the N lightsignals towards the holographic combiner effectively from respectiveones of the N spatially-separated virtual positions for the scanninglaser projector, the particular virtual position for the scanning laserprojector from which each one of the N light signals is redirected bythe optical splitter determined by a respective point of incidence atwhich each light signal is received by the optical splitter, and whereinthe holographic combiner comprises at least one hologram positioned andoriented to converge each one of the N light signals to a respectiveexit pupil at or proximate the eye of the user.
 16. The wearableheads-up display of claim 15 wherein the N light signals include Ndifferent instances of a same image.
 17. The wearable heads-up displayof claim 15 wherein the N light signals include N different instances ofa same pixel of an image.
 18. The wearable heads-up display of claim 1wherein the optical splitter comprises a faceted optical structure withat least N facets, and wherein at least one respective facet correspondsto each respective one of the N spatially-separated virtual positionsfor the scanning laser projector.
 19. A wearable heads-up displaycomprising: a support structure that in use is worn on a head of a user;a scanning laser projector carried by the support structure and having atotal two-dimensional scan range θ including a total scan range Ω in afirst dimension, where 0°<Ω<180°; a holographic combiner carried by thesupport structure, wherein the holographic combiner is positioned withina field of view of an eye of the user when the support structure is wornon the head of the user; an optical splitter carried by the supportstructure and positioned in an optical path between the scanning laserprojector and the holographic combiner, wherein the optical splittercomprises at least one optical element arranged to: receive lightsignals corresponding to a sweep of the total two-dimensional scan rangeθ by the scanning laser projector; separate the light signals into Ntwo-dimensional sub-ranges φ_(i) based on point of incidence at theoptical splitter, where N is an integer greater than 1 and${{\sum\limits_{i = 1}^{N}\varphi_{i}} = \theta};$ and redirect thelight signals towards the holographic combiner, and wherein theholographic combiner comprises at least one hologram positioned andoriented to converge light signals to respective ones of N exit pupilsat or proximate the eye of the user, the particular exit pupil towardswhich a light signal is redirected by the holographic combinerdetermined by the particular two-dimensional sub-range φ_(i) into whichthe light signal is separated by the optical splitter, and wherein atleast one element of the optical splitter is arranged to: receive lightsignals corresponding to at least one sweep of the total scan range Ω inthe first dimension by the scanning laser projector; separate the lightsignals into X sub-ranges ω_(i) in the first dimension based on point ofincidence at the optical splitter, where 1<X≤N and${{\sum\limits_{i = 1}^{X}\omega_{i}} = \Omega};$ and redirect the lightsignals towards the holographic combiner, and wherein at least onehologram of the holographic combiner is positioned and oriented toconverge the light signals to respective ones of at least X of the Nexit pupils at or proximate the eye of the user, the determined by atleast the particular sub-range ω_(i) in the first dimension into whichthe light signal is separated by the optical splitter.
 20. The wearableheads-up display of claim 19 wherein the total two-dimensional scanrange θ of the scanning laser projector includes a total scan range ψ ina second dimension, where 0°<ψ<180°, and wherein at least one opticalelement of the optical splitter is arranged to: receive light signalscorresponding to at least one sweep of the total scan range ψ in thesecond dimension by the scanning laser projector; separate the lightsignals corresponding to the at least one sweep of the total scan rangeψ in the second dimension into Y sub-ranges β_(i) in the seconddimension based on point of incidence at the optical splitter, where1<Y≤N and ${{\sum\limits_{i = 1}^{Y}\beta_{i}} = \Psi};$ and redirectthe light signals corresponding to the at least one sweep of the totalscan range ψ in the second dimension towards the holographic combiner,and wherein at least one hologram of the holographic combiner ispositioned and oriented to converge the light signals corresponding tothe at least one sweep of the total scan range ψ in the second dimensionto different ones of the N exit pupils at or proximate the eye of theuser, the particular exit pupil towards which a light signal isredirected by the holographic combiner determined by both the particularsub-range ω_(i) in the first dimension and the particular sub-rangeβ_(i) in the second dimension into which the light signal is separatedby the optical splitter.
 21. A method of operating a wearable heads-updisplay, the wearable heads-up display including: a scanning laserprojector that includes a red laser diode, a green laser diode, and ablue laser diode; an optical splitter, and a holographic combinerpositioned within a field of view of an eye of a user when the wearableheads-up display is worn on a head of the user, wherein the holographiccombiner is a wavelength-multiplexed holographic combiner that includesat least N multiplexed red holograms, at least N multiplexed greenholograms, and at least N multiplexed blue holograms, the methodcomprising: generating a first light signal by the scanning laserprojector, the first light signal including a red component, a greencomponent, and a blue component; receiving the first light signal at afirst point of incidence by the optical splitter; redirecting, by theoptical splitter, the first light signal towards the holographiccombiner effectively from a first one of N spatially-separated virtualpositions for the scanning laser projector, where N is an integergreater than 1, the first virtual position for the scanning laserprojector from which the first light signal is redirected by the opticalsplitter determined by the first point of incidence at which the firstlight signal is received by the optical splitter; and converging thefirst light signal to a first one of N exit pupils at or proximate theeye of the user by the holographic combiner, wherein converging thefirst light signal to a first one of N exit pupils at or proximate theeye of the user by the holographic combiner includes: converging the redcomponent of the first light signal to the first exit pupil by one ofthe at least N red holograms, the one of the at least N red hologramsdetermined by the first virtual position for the scanning laserprojector from which the first light signal is redirected by the opticalsplitter; converging the green component of the first light signal tothe first exit pupil by one of the at least N green holograms, the oneof the at least N green holograms determined by the first virtualposition for the scanning laser projector from which the first lightsignal is redirected by the optical splitter; and converging the bluecomponent of the first light signal to the first exit pupil by one ofthe at least N blue holograms, the one of the at least N blue hologramsdetermined by the first virtual position for the scanning laserprojector from which the first light signal is redirected by the opticalsplitter, wherein the first exit pupil to which the first light signalis converged by the holographic combiner is determined by the firstvirtual position for the scanning laser projector from which the firstlight signal is redirected by the optical splitter.
 22. The method ofclaim 21 wherein the holographic combiner includes awavelength-multiplexed and angle-multiplexed holographic combiner thatincludes at least N angle-multiplexed red holograms, at least Nangle-multiplexed green holograms, and at least N angle-multiplexed blueholograms, and wherein: converging a red component of the first lightsignal to the first exit pupil by the at least one red hologram includesconverging the red component of the first light signal to the first exitpupil by a first one of the N angle-multiplexed red holograms, the firstangle-multiplexed red hologram by which the red component of the firstlight signal is converged determined by the first virtual position forthe scanning laser projector from which the first light signal isredirected by the optical splitter; converging a green component of thefirst light signal to the first exit pupil by the at least one greenhologram includes converging the green component of the first lightsignal to the first exit pupil by a first one of the N angle-multiplexedgreen holograms, the first angle-multiplexed green hologram by which thegreen component of the first light signal is converged determined by thefirst virtual position for the scanning laser projector from which thefirst light signal is redirected by the optical splitter; and converginga blue component of the first light signal to the first exit pupil bythe at least one blue hologram includes converging the blue component ofthe first light signal to the first exit pupil by a first one of the Nangle-multiplexed blue holograms, the first angle-multiplexed bluehologram by which the blue component of the first light signal isconverged determined by the first virtual position for the scanninglaser projector from which the first light signal is redirected by theoptical splitter.
 23. The method of claim 21, further comprising:generating a second light signal by the scanning laser projector;receiving the second light signal at a second point of incidence by theoptical splitter; redirecting, by the optical splitter, the second lightsignal towards the holographic combiner effectively from a second one ofthe N spatially-separated virtual positions for the scanning laserprojector, the second virtual position for the scanning laser projectorfrom which the second light signal is redirected by the optical splitterdetermined by the second point of incidence at which the second lightsignal is received by the optical splitter; and converging the secondlight signal to a second one of the N exit pupils at or proximate theeye of the user by the holographic combiner.
 24. The method of claim 23wherein: the scanning laser projector has a total scan range θ;receiving the first light signal at a first point of incidence by theoptical splitter includes receiving, by the optical splitter, the firstlight signal at a first point of incidence that is included in a firstone φ₁ of N sub-ranges φ_(i) of the total scan range θ for the scanninglaser projector, where${{\sum\limits_{i = 1}^{N}\varphi_{i}} = \theta};$ redirecting, by theoptical splitter, the first light signal towards the holographiccombiner effectively from a first one of N spatially-separated virtualpositions for the scanning laser projector, the first virtual positionfor the scanning laser projector from which the first light signal isredirected by the optical splitter determined by the first point ofincidence at which the first light signal is received by the opticalsplitter includes redirecting, by the optical splitter, the first lightsignal towards the holographic combiner effectively from a first one ofN spatially-separated virtual positions for the scanning laserprojector, the first virtual position for the scanning laser projectorfrom which the first light signal is redirected by the optical splitterdetermined by the first sub-range φ₁ of the total scan range θ for thescanning laser projector; receiving the second light signal at a secondpoint of incidence by the optical splitter includes receiving, by theoptical splitter, the second light signal at a second point of incidencethat is included in a second one φ₂ of the N sub-ranges φ_(i) of thetotal scan range θ for the scanning laser projector; and redirecting, bythe optical splitter, the second light signal towards the holographiccombiner effectively from a second one of the N spatially-separatedvirtual positions for the scanning laser projector, the second virtualposition for the scanning laser projector from which the second lightsignal is redirected by the optical splitter determined by the secondpoint of incidence at which the second light signal is received by theoptical splitter includes redirecting, by the optical splitter, thesecond light signal towards the holographic combiner effectively from asecond one of the N spatially-separated virtual positions for thescanning laser projector, the second virtual position for the scanninglaser projector from which the second light signal is redirected by theoptical splitter determined by the second sub-range φ₂ of the total scanrange θ for the scanning laser projector.
 25. The method of claim 21wherein generating a first light signal by the scanning laser projectorincludes generating a first instance of an image by the scanning laserprojector, the first instance of the image including at least twopixels.
 26. The method of claim 21 wherein generating a first lightsignal by the scanning laser projector includes generating a firstinstance of a first pixel of an image by the scanning laser projector.